Hrm. Labour was vastly unpopular. The biggest power move the LibDems could do was install preferential voting (which would harm the two party system by allowing eg
1 minor party
2 major party
3 other major party
...preference votes), and the British public (stupidly, but that is their decision) rejected it. He couldn't eg freeze tuition fees because the LibDems were a junior partner in the coalition. The vote on preferential voting was far more significant, if the LibDems could pick one of the other, it was right to pick preferential voting.The British public blew it, because they bizarrely chose to have less of their own voting intentions recorded.
But that’s not the reason he got elected. He got elected because he promised to end student loans.
If someone says to you, “I’m going to take your money and bet it all on black on the roulette table.” and then comes back and says “sorry I lot it all because I bet it all on 22,” you’d be pissed! Now imagine they come back and say “not only have I lost it all but I borrowed an additional 3x in your name and also lost that”.
AV was an absolute non issue to most voters who elected them. Student debt was no1. Doesn’t matter if you think you know better than the people who elected you, it was a stupid gamble.