@Viridios fenrir doesnt start ragnarok his bindings just stop existing since near the start of ragnarok all restraints break which is why both him and loki get free
ragnarork starts with three winters without summer and brothers killing brothers and others calamities then all the restraints break and various giants arrive from the south and east
tyr's part in fenrir's binding is more him being stupid enough to offer his hand as colateral if they didnt take the binding off at the end of the test of strength
but the story we know is supposedly like the 12th or something ragnarok as it was a cyclic thing with the end being the creation of a new realm
@Angibot power of prophecy maybe, like that tyr and odin's deaths to fenrir are fortold so even if the gods win the main cast of the gods all need to be re-incarnated since they are all fated to die and this same act has played out many times now