There are lots of reason and circumstances why developers decided to stop a project. I remember one project before,i was hired as a community manager and after like 4 months there is no progress and they had been scammed by their marketing director so the team decided to stop the project coz they are losing a lot of money.
One common reason is lack of budget. It will be hard for a project to succeed if you only have a minimal budget for it.
It's quite unfortunate that even a party to the project, ripped the project of funds. The issue of budget and finance seems to be predominantly a factor for legitimate projects closing down. It feels really terrible to have a potential great project get abandoned because of finance and distress within the team.