Not sure if it was suggested already or not, but one option is to look for “lets play” style videos for some game (gonna be hard to find one that’s simple enough, probably) and take the spoken text the youtuber says as thoughts. Some of them already have the transcript as subtitles.
On the same vein, looking for people who explain their choices in very clear-decision games, like chess. I once saw a booklet of chess games where the actual player explained most of his moves. If there is a way to get many of those, that might work.
The problem with commentary not made by the players themselves is that, as far as I understand it, the project wants the general thoughts of the player and not just the motivations for every specific move. Like, ideally, they want some stream of consciousness commentary style “oh look, that guy looks kind of tough, I’ll go see if I can agro him. Oh no! he’s way too strong… lets go hide behind this tree it looks kinda safe [...]”. That’s why I suggested the lets plays and not e-sports in general.
If they’re ok with just noise-free motivational analysis, anything with good commentators might work, and chess is indeed a pretty clean option.