Without knowing the details, the fact that multiple core developers quit seems to be some evidence that they were treated unethically. That's not something that happens in normal conditions.
Timing is vital in these contexts. I've worked at a job in a team of 3 under terrible conditions (terrible from a "western" perspective of course, nobody was whipping or pointing guns at us, but you get the point). Complaining with management -the worst bunch of incompetent idiots I ever encountered in my life- was 100% ineffective so that after just a few months one of my colleagues left, then a bit later I left. The company suddenly panicked realizing how the project was likely going to tank in a spectacular way and promptly turned their tactics literally burying the only left member with money, benefits and much better working conditions so that he kept the job for years. Same company, same project, same team, but asking to 2 different people could have yielded very opposite opinions.
