Typically, the amount of grant money you receive does not affect your salary. It can affect your job security and it can be a factor in earning tenure, but in general, writing more grant proposals=/=higher pay (just more money for research).

Plus, even at R1 schools, tenure-track positions are often starting out with pretty low pay compared to tuition and very low compared what the professor could be making in private industry. According to this study by National Center for Educational Statistics, only about a third of college budgets are spent on instruction, with about another third on support services (counselors, financial aid, tutoring/library services, accessibility services, etc.), with the remainder spent on administration. But that doesn't look so bad until you realize that at most schools, 50%-75% of the courses are not taught by full-time instructors, but by adjuncts, and adjuncts are often paid at or below the poverty line (about 25k/year in 2020). Even as a tenured instructor with 10 years of salary schedule advancements and a partner with a full-time job in higher education, I'm still living paycheck-to-paycheck.

So, yes, it is more complicated than "all professors are underpaid," but not by much. It's really more like "75% of college instructors are near or below poverty level."