Did [St. Thomas's] gift of great intellect (surely predisposing him to appreciate reason) color his doctrine? Or did his doctrine color his behavior and nurture his intellect (i.e. give him the desire and industriousness necessary to write something like the Summa)? Maybe some of both though it's probably unfair to speculate.
The way I'd put it -- and I put it in a post rather than a comment both to increase the chance of correction and because this beats the topic I was going to write about today -- is that St. Thomas's great intellect certainly colored the way he expressed his doctrine. A reader can be excused if he gets the incorrect impression that the intellect is the be-all and end-all of St. Thomas's doctrine. The Angelic Doctor gave a lot of theological avenues only the briefest of sketches. If you were to say there are whole boulevards of which the best that can be said is that his intellect-centric perspective didn't brick them off entirely, I wouldn't dismiss you without a hearing.
At the same time, it was his intellectual vision that allowed St. Thomas to see where the human intellect fits in relation to God and creation. And if a thing fits in relation to other things, if it has a place, then it necessarily has boundaries, and there are places where it is not.