You are so wrong.
Linux kernel is a monolithic kernel what means Linux kernel is the complete operating system. There is no other software needed to add to have full operating system than just the Linux kernel.
Same thing is with FreeBSD, OpenBSD etc what are all using a monolithic operating systems architecture, not the Server-Client operating systems architecture like XNU and NT, operating systems of OS X, iOS and Windows, Windows RT and Windows Phone.
XNU operating system does have servers from FreeBSD, but the whole XNU operating system or most important part of it, the microkernel, is not from FreeBSD. The Apple toke network stack and filesystems functions from a FreeBSD and made them operate as servers instead modules and used them in XNU.
Linux has conquered the world. It is used in most servers, most embedded systems and in most mobile devices from smartphones to now tablets. Linux operating system is most used operating system in the IT history by its wide usage purposes instead being just targeted to specific use (like only on embedded systems). Linux has proofen that monolithic operating system architecture is superior to server-client (aka microkernel) architecture in security, speed and stability. Because its open licensing and huge community, Linux hardware support and level is second to none. The Linux operating system is licensed under GPLv2 and it secures its openess (even that some would like to it be GPLv3 or BSD) and it truely was the most important decision what Linus Torvalds made, to use GPLv2 instead own or other license.
Linux deserves the credit for being most used operating system. It has already passed the install base of Microsoft or Apple developed operating systems by two fold, thanks to mobile world. Thanks to Linux, we have truely a open operating system used in the world, what is requiring hardware and software developers to take Open Source seriously, even Microsoft admitting that Linux operating system is more widely used and Open Source isn't "a cancer" or threat to industry jobs.
Every success what Android gets, is success for Linux as it is the operating system in Android. It isn't even directly success to Google either, because Android is developed by Open Handset Alliance (OHA) what is lead by Google. Every OHA member is free to improve Android and send patches. But Google makes sure that Android AOSP stay clean from proprietary code or functions what would benefit only a single authority.
Many falsely believes that Google applications and services (gapps) belongs to Android, while they don't. Google applications framework and all applications are third party to Android like Samsung S-series software is for Android or Microsoft software for Android is third party. The difference is just with the Google that if you want to call your device as Android device, you need to be OHA member and then pre-install only the Google Play (not required to install Google Maps, Gmail or any other applications for Google services) and you are free then to install any alternative services for Google services, but you can not block device user from installing any other third party (including Google Maps, Google Search or Gmail) applications and make them as default instead your chosen ones.
You are as well required to not modify Android API/ABI so that you don't have 100% Android compatibility. And here is again the other mistake what people make, as Hardware differences (display, resolution, CPU, GPU, amount of RAM, camera, flash, microphones, compass etc etc) are the one what you are free to design and use as OEM. And if Android application developer has designed their application to need hardware functions like front camera and rear camera flash, then if you have cheap Android device what is missing both, you can not see or install that application from Play store because your hardware doesn't fill the requirements the application developer has chosen to. It isn't fault of Android or it doesn't require application developer to test their software on every individual Android device model. Only require thing is to follow Android guidelines and use specific API level (like 14) and then hardware requirements like camera or OLED display. Android knows what hardware features it has and sends that information to Play what then by your handset tied to your Google Account filters Android applications based the requirements. So if you have Tegra 3 in your handset and game developer has used features what are available only in Tegra 4 and optimized the game for that SoC, then using your handset to browse games from Play store, it doesn't see the game as it is incompatible with your handset.
Linux operating system, like any operating system is no use for the user. It is the directly something important for hardware manufacturer. The Android hides Linux operating system with Dalvik Virtual Machine. You don't as software developer care anything about Linux operating system in Android as you don't have access below Dalvik. As a user you don't use operating system but you use the user interface of the device, the hardware (volume rocker, power button, camera button, display, casing etc) and the software (launcher, applications etc). As a user you don't use operating system (in any system) or you don't see operating system (in any system). (required car analogy) As operating system is like a car engine, when you are driving on highway, you don't operate the engine or see the engine, you operate controls like pedals and gear stick and they deliver commands to engine and other car parts.
For many people t is very hard to Get It, that Linux is huge success and very widely used. Because they only believe what they have seen. That Linux is same thing as KDE, GNOME, Unity and so on. And because they don't see those, "it ain't Linux as Linux is just a kernel!!!!!".
Android Inc chose to use Linux as the operating system in Android. When Google bought Android Inc, they kept using Linux because they already knew it. Google has lots of Linux engineers and experience because they use Linux operating system in their servers and systems. They knew for what the Linux is capable and what can be made from it with support of community and legally.
If Android would not have Linux as its operating system, I would bet that Android would not be at all same kind success. Like think if Android would have a proprietary operating system what isn't used anywhere else? Hardware manufacturers would hate to write drivers and functions to every new chip separately or license them all from manufacturers. OHA would need to design and maintain alone their own operating system and it isn't easy task at all. With help of Linux community, thousands of talented operating system hackers and engineers are tweaking and improving Linux every day, leaded by Linus and his "generals". But as it is open source, OHA can keep own functions like Wakelock if they think it is better than what is available. And that is possible because Linux kernel is the Open Source Operating System.