C is a very small language with a modest standard library. The language itself has ANSI and ISO certifications. The standard C library is largely defined by POSIX. I con't have to hold much in my head by way of language constructs or reserved words, etc. and any other programming languages derived their syntax from C, so it will get reenforced often (except the weird ways to use pointers).
If I have a question about a standard libc function, the man pages will be there on my systems whether it is FreeBSD, Solaris or Red Hat. Most of the time, a question about C can be equally expressed as a question about Unix-like systems because of this.
C and POSIX are well established and have been through a rigerous standards process, so unless you're interested in a fancy new compiler feature like SafeStack on clang/llvm, you don't really have a lot to learn or relearn once you have it down. No one is about to change how C represents strings or any of the like between versions of compilers for reasons of "just because," though. You may need to look up the specifics of a third-party library if it didn't come with man pages, but that might not show up as a search about C.
Other languages with huge base libraries which aren't part of the OS's standards definition, multiple programming paradigms, lack of standards causing if shifts between versions, etc., are almost certainly going to get more people heading to Google because they have to.