Aguably those things would have happened with or without a union. E.g. it's extremely rare that any studio could repeat a masterpiece like Witcher 3, and CDPR's earlier Witcher titles also are far away from that quality. This game really was a unique 'perfect storm'.

From what I've seen, success and following decline are directly related. Once a studio becomes successful, they start to attract the sort of people (especially in leading positions) who are great at selling themselves but not much else, and the studio founders haven't learned yet to separate the chaff from the wheat. And then after a while suddenly the company is full of 'mercenaries' which only care about their own carreer advancement but not about the games they create.