OP says 18 months and Gust was waiting for annual bonuses and stock to mature.

As you say, you chose to coast at your own job as a reasonable and fair response. You did the work you were contracted to do and got paid correspondingly. Yeah you’d have liked a promotion path to a more demanding and rewarding role, but that’s just not something your employeer needed/wanted.

Lots of jobs aren’t our perfect dream jobs. But I assume you started looking in the meantime, and when you did find a job which better fit your ambitions you moved on, and did so in a professional manner which ensures your own professional reputation stays intact.

Gust just burnt the world; took his own pain and paid it forward. Victim (partly self-made) becomes an abuser himself. Sorry, no, I’m going to call that.