Funny bridge burning

Howdy, Blinders, just want to share my story. I landed to at job at startup 6 months ago (TC ~ 400K - salary+stocks and a sign-up, which I should pay back if I will leave in 1 year, pretty standard terms). Unfortunately, I got a workaholic boss. Two weeks passed, and he called me and said, that when he was starting on his job here, he worked 16 hours per day to catch up faster. I said, that it was his choice, and I really admire his dedication, but I really do not see myself doing more that I was obliged in contract (with some exceptions in case of emergency). Long story short, 90 days passed (they was full of 1-on-1's with unhappy boss, his comments about his uncertainty about my capabilities), and I was told that I failed probation. CTO (it's a skip-level boss) invited me to meeting, where he said that they can offer me position in another team with lower salary. I said no, I'm not going to reduce my expectations, we talked a little bit, with HR involved. They said that they will offer me the same compensation, but I need to quit and join again to be on probation again (it's was because of their internal policies). I said ok. So, I'm leaving by mutual agreement, joining again, passing probation on another team. But I felt really not happy - it was like I lost excitement about this company (and lost 3 month of vesting, etc... ). So, I opened my contract, and it turned out that I can leave without paying back sign-up (because of mutual agreement leaving). So I left. Well. It was really hot there, HR was trying to convince my to return bonus, then she was ok if I return only half of that. CTO was angry (or pretended to be), promised bad references. But... I was doing legal thing here. What do you think? Was this fair?