What really happens to a crypto coin if trust in the ledger is shattered?

Does the coin stay alive purely because people still speculate on hype or does everyone try to cash out simultaneously and send price into a death spiral?

Shattered is the trust in transactions that happened during the time period where the attacker controlled >51%, from addresses that the attacker also controlled. AFAIK so far they haven't controlled 51% for any amount of time, though they did control more than 33% for a short while, which is enough for "selfish mining." Either way, the attack did illustrate that a government could easily take over XMR if they wanted to. The impact of that, we'll have to wait and see.