except when you moved to C there was no corresponding increase in fixed time which you must spend on tool setup just to program

Yeah, it’s really great that compiling C is a straightforward endeavor that doesn’t require any tools, and definitely doesn’t depend on executables that generate or parse configuration files. I’m confident that no C developers have ever spent time on tool setup just to program.

gcc main.c

Of course tinkerers made some tools you can tinker with as time went on, but you don’t have to let those interfere with velocity, just like I will not be using configuration languages.

Do you mind linking me to some large C projects that don’t use make/autotools/etc?

stb libraries

So… novelty single-file libraries? I’m not sure that “it works if you only have one file” truly supports your argument.