In all seriousness though, there's been a combination of stupidity that's created the conditions for Johnson.
- Iraq has nobbled Blair's legacy, so nobody listens to him on anything else;
- Clegg backtracking on his manifesto and going into power with the Tories gave them a free pass the following election;
- Add to that him not liking Brown so not even entertaining a Lib-Lab coalition at the time;
- Both Blair and Lib Dems being discredited meant voices against Brexit were diminished, lacked credibility, and couldn't carry people along.
So here we are, when a fair few who voted Lib Dem can't again for the foreseeable, even if some of their policies align with their own beliefs, because the betrayal was enormous. That's given the Tories a free ride in some places, and allowed them to focus on other areas as a result, and take seats from Labour where they normally wouldn't.
Add to the fact that nobody within Labour will now listen to Blair on how to win an election, despite the fact he's the only one to manage it, and you have an opposition divided between the legacy MPs who were around at his time, the newer intake, and the party members - meaning they're doomed to be ineffective as long as they don't all come together in some way, whoever the leader is (be it Corbyn, Starmer, or Donald Duck).