I think the reason it is working and has worked so far is aligned incentives - doing something nefarious or selfish will ultimately work against you as people abandon and avoid you.

There is no doubt though that cryptocurrencies are potentially fragile. I do think though that pandora's box has been opened. Maybe bitcoin will stand the test of time like jpeg, C, C++, http, TCP/UDP/IP, zip, bittorrent, fortran, x86, SMTP, unix, RTSP, vi, javascript, etc that have been good enough and persisted with a huge network effect. Or it could end up being a jumping off point for something that smooths out the rough edges needed for mass adoption.