Patrick Stewart did something kind of incredible during his TNG run. Shows like that didn't do serial plots back then; show execs wanted everything to be back to how it was after the show so people could jump in and jump out and they could syndicate freely.
So playing the few persistent evolutions of his character there were required an almost two-faced approach where the character is fine and unchanged most of the time, then suddenly very isn't when it's pertinent. In such a way that you question if you just missed signs of that evolution all along, too.
Picard was traumatized by several events in the show: spending what he felt was an entire lifetime as someone else, being captured by the Borg and Wolf 359, falling in love with someone and finding he couldn't be a fair and effective captain with her safety on the line...
He had tiny cracks to open the door and expose the inner workings of the character when they became pertinent again, and led to some of his best moments on the show; like his link in the chain speech.
It's almost comical in a way that you might only notice these little things in a binge watch. A couple of his "Locutus" throwbacks were very obvious though.
You'll find after him, DS9 and Voyager were far more willing to play with multi-episode evolutionary arcs. I can only imagine that would not have happened if TNG didn't go so well.
I guess what I'm saying is he wasn't just a hell of an actor; he transcended and pushed forward the medium when he was most active in it.