Indexing and quarantine issues are the same. It is an automatic system that puts games into a waiting queue for human staff to have a look. That can and does happen to already indexed projects. Every update can trigger temporary deindexing and even quarantine.
The problems arise, because waiting times are weeks instead of days.
Do not expect an answer to this. Imagine how Itch would tell scammers exactly what they did do trigger the automatic system...
For quarantine, the system might suspect that your account could be hacked. Maybe it is as simple and obscure as an internet capable device in your home network being hacked and used as a bot device in ddos attacks. Itch was very likely attacked again the last day. And there are things like Badbox with literal millions and millions of devices that even had the malware preinstalled.