The Tony Blair argument rather falls flat if you ask yourself what would have happened if John Smith had led the party in 1997.
Or does he not count either :-)
The Tory party has always been good at reinventing itself, Labour less so.
But as has been said many times before, both Labour and the Tories have been written off as finished before.
Not so long ago the Tories hadn’t won an election outright since 1992. And after the Euro elections they were supposedly dead.
2019 was an odd election, not only for being held near Christmas. But also there were effectively two opposition parties running for power. Johnson managed to dissociate himself from the previous Tory leadership. Successful reinvention.