Petrarch was apparently fascinated throughout his whole life by Cicero, in a way that his contemporaries apparently weren't. He even wrote letters to Cicero. But these letters don't mean much to me, other than displaying Petrarch's incomparable obsession.
In Petrarch's time intellectuals had many letters to read from great men past and present, and mountains of Christian theology to devour in pursuit of divine truth. So what made Petrarch so disinterested in the mainstream of medieval thought, and fascinated by Cicero in particular?
I'm completely clueless about secondary literature, so if you have any books to recommend that would help clarify this, I'd be just as happy to read them as a standalone answer.