I have seen nepotism first hand so I know it is a real thing. But in the same time I also have been in situation where I hated a manager from another division

I have seen nepotism first hand so I know it is a real thing. But in the same time I also have been in situation where I hated a manager from another division who was clear he wanted to take over my team. I did not manage those emotions well enough, and they were easy to exploit. Also the fact that the guy was having regular evening phone calls with people from my team, led to creation of very toxic situation. People can be very methodic when they really want to achieve something, in such situation you are either more methodic or you submit to the situation. In such situation a lot depends on who you can talk to in your workplace and what is their position in hierarchy. I'd advice you calm down and make a mental work of decoupling your life at work from emotions you experience. Make yourself a list of priorities that you want to achieve and work towards achieving them in a well planned way. If making more money is one of them then you need to have plan B which you can fall back if/when you don't get that in your current place. If having nice environment at work is another item on your list then you want to work around your emotions/ambitions or jump to another company. I personally would start making moves to leave as soon as I was asked to train my replacement. But again the situation is probably a bit more complicated than you think it is - or maybe it is not? :) Good luck.