I'm sure those writers were quite content writing for an actor of that calibre. Imagine putting words to the page, knowing Patrick Stewart will take them out into the world and surely stick the landing.
What a great combination.
We know Stewart was not a great writer, of course. When he had opportunities to take the reigns of the Picard character creativitely he usually asked for more action, and the results were a bit more conventional and boring. The combination was certainly also needed for the magic.
I always liked this video from an acting workshop where Suchet and Stewart deliver contrasting performances of Shylock and discuss their choices at length:
It's an actor's job to dramatise our projections, so from that POV he did a legendary job with TNG.
But there's a certain amount of learned skill involved. I know someone who used to work backstage at the Royal Shakespeare Company. She said that she'd all these famous names playing cards backstage, they'd get their call, turn on the juice, stride on stage, say their lines with the appropriate presence and gravitas, then turn the juice off again after the scene and pick up the card game where they left off.
Stewart's choice of roles and support for causes suggests there was more than that involved for him.
He wasn't Picard in real life, but he wasn't just acting either.