Can two goblins move onto a crystal tile and smash it in the same turn?
I think the answer is no, but thought I'd make sure.
I think in general the answer is yes. The key thing is that attacking a crystal is an action, so if they do any other sort of action they cannot. But flare is not an action - it is part of the movement.
So one tribe moves onto the crystal and attacks it. Nothing happens.
Then the second tribe moves onto the crystal and attacks it. Then it is smashed.