This pope had been his patron, and despite his knowledge, Galileo was in many respects a blustering fool. Bellarmine, who had protected him, tried to warn him not assert what few educated men of his time believed, which was that mathematics was a true measure of things in general.
It took a century and a half for the "educated" Romanists to slink off, tails between their legs, and quietly remove his book from the Index.
By then, of course, they were nothing more than a laughing stock. It took 3½ centuries for the highly "educated" Church of Rome to [sort of] apologize. Unfortunately, during all of those three hundred and fifty years, the "fool" was correct and the highly "educated" clerics of the Vatican, who believed mumbojumbo was a substitute for mathematics, science, and reason were ... completely, utterly, and, dare I say infallibly ... WRONG.
If Galileo was a "fool" what does that make the Magisterium?