It's been an ongoing process and the timing is almost 100% related simply to the timing of their contracts running out, not anything actually happening
TL;DR - right as the ID branch started to get momentum in Indonesia, participating in events, getting merch, establishing connections, Nijisanji decided they are not making enough and not quick enough money, canned the whole thing, merged them into JP branch, leaving them with nothing but a skeleton crew in terms of support and deploying the classic JP tactic "we will not fire you, but we will make your life miserable so you leave on your own"
Also ID really liked their management (as absurd as it sounds) and thought they were putting 200% into making sure it's a success, despite Hana's best efforts. They had nothing but good things to say about them and losing all of this support in exchange for nothing but a spit in the face must've been a horrible experience.