Your question was not posed to me, and of course opinions will vary.
If you ask me, it isn't possible to reach PM without an ego which is outsize to what is usual, then it tends to grow with observable complacency. A large parliamentary majority cements the idea in the egoist that everybody loves them. That's why narrow majorities and a few losses in the voting lobbies helps to apply an inward pressure to the otherwise ballooning ego.
Blair wanted to go along with Bush's false dichotomy of 'you're either with us or against us' because his ego wanted the world to see he was playing in the big boys game at the big boys table.
Personally I think Blair deserved to be committed to jail for his part but the offence of Misconduct in Public Office did not exist at that time, but followed along shortly after in 2003.
I remember on hearing Robin Cook's wonderfully eloquent and heartfelt plea in his cabinet resignation speech, and the impassioned speech from Tony Benn, that parliament could not in good faith vote for war, but they did. The Tories love to condemn Blair, but how quickly they think we will forget how they played their part - they voted for it too, despite Cook at least alluding to the fact that Blair was lying.
Continuing the ego theme, and people might understand my objection to Johnson ever becoming PM, and my fear that a big majority would inflate his ego further with the result of damaging the country. I feared that if the USA went to war with Russia that Johnson with his Churchillian pretensions would drag us quickly into a war that escalate to world war.
Maybe what we need is a limit to the number of years a PM can serve in the UK as in other places?