it is possible for someone to be dumb and yet to have good verbal skills.
one can sound articulate by simply being able to repeat what they have heard. on the other hand, analytical skills are needed for deductively reasoning and that is what it seems garrett is sorely lacking.
look at what he did in getting into princeton/columbia (
https://en.wikipedia.org/wiki/Jason_Garrett#College_career):
"Garrett was accepted to
Princeton, where he began as the starting
quarterback of the freshman team, registering 64 completions on 116 attempts for 996 yards. He transferred to
Columbia University when his father,
Jim Garrett became the
head coach in 1985. Following his father's resignation after Columbia's 0–10 1985 season, he and his brothers (
Judd and
John) transferred to
Princeton University, although none played varsity in 1986 for different reasons (Jason was an ineligible transfer)."
what that tells me is that garrett was able to play politics/connections at a young age. he was clearly taught/able to leverage his father's position and his football talents to get accepted to princeton, transfer to columbia and back to princeton. nobody transfers out of a college and back in. so he is a skilled politician. so he is plenty good at putting on knee pads and giving the jones their jolly.
now intelligence includes verbal skills, but also has things like deductive reasoning and 3d spatial skills. and it is deductive reasoning and 3d spatial skills that are needed for creating good schemes and making good decisions. these are needed for what you call football sense. these intelligence components are what garrett is apparently sorely missing.
so i thereby double-down, garrett is simply dumb based on what we have seen in the 8 years of discontent.