Pascal, especially the versions running on the UCSD P-Systems, was once the largest install base of computer software.
Your analysis is wrong. No one really knows why C displaced Pascal, in fact I would say, it was not C but C++.
My judgement is that the high costs of Eiffel and Ada compilers/envirnomnets helped C++ to pave the way.
Around that time (1990 - 1995) we also had a rise of OO and CASE and modeling methods (OMT, Booch etc. and later UML). I assume the focus of modeling tools on SmallTalk and C++ and very soon Java (1997) made it even more troublesome for Pascal.
Back stage the Pascal companies where canibalizing themselves. The winner, the company buying or destroying the competition, simply did not last and got sold, bought out or whatever ... they simply vanished.
The same with C#, the language only exists because MS made a mistake in their EEE policy regarding Java. The arguable benefits of one language over the other where established an half or a full decade later. (None had generics or lambdas when developed ... etc.)
C never had a hughe standard library, it still has not till to our days. so this argument makes no sense at all. Even C++ still lacks standard threading and standard GUI libraries ... I guess one or the other is now addressed by boost and Qt ... but like Apache for Java, this are third parties.