There were portability issues with C compilers, for example, value preserving vs sign preserving integer promotion rules.

But Pascal was unusable without extensions. I mean that. I wrote programs in Pascal.

For example, Wirth's Pascal had no provision for programs that had more than one source file.

I wouldn't consider RatC or Small-C that usable without the pile of Assembly code they needed to be usable beyond bare bones control flow statements.

Like I say, two weights two measures.

Nothing was non-trivially usable on an IBM PC without a pile of assembly code.

Integrating C with assembly was easy. Pascal originally didn't support that at all. And academics were utterly horrified by things like Turbo Pascal.

The usual argument, C extensions for inline Assembly and dialects outside UNIX, no problem, it was great.

The fact that Pascal extensions existed, and Modula-2 as evolution from Pascal was a standard since 1978, doesn't count.

Even the bad early C compilers were far more usable than Pascal. I know this, because where I worked at Data I/O we tried a whole bunch of them - Pascal, Fortran, and C.