He's never really gone away. When Brexit looked increasingly inevitable and the Brexit party started making gains, Blair was stirring on the periphery talking about getting back into politics to try and prevent catastrophe for him and his globohomo EU goons.

You can attribute Corbyn's destruction largely to the Blairite/Corbynista split in that party, where types like Blair, Mandelson and Alastair Campbell have remained active prodding the Labour party and the media via their channels from the shadows. It's not too dissimilar to the Clinton cabal vs Sanders struggle in the US, with the neoliberal warmonger establishment always poised to win against naive socialist old coots.

Blair makes me want to fucking puke, but he got a standing ovation from all parliament when he stepped down from PM, which shows how cucked both sides of the aisle really are. The public can do nothing to prevent his vile rictus from repeatedly being shoved onto screens long past the point when he should have been politically neutered, just another symptom of how fucked the country is and how much the populace is held in contempt by its ruling class.