So far as I can see, that's not what happened at all. Let's ignore Scotland/Wales/NI and look at what happened in England (using the BBC results here.
The Lib-Dems lost 37 seats. Labour are up 15, Conservatives are up 21. And as they'd only been 20 seats off of a majority in 2010, that was enough to win them the election.
Labour's vote share in England actually increased by 3.6%, larger than the Conservative increase (1.4%) - but that didn't matter, because the Conservatives (a) grabbed more of the Lib-Dem/Tory swing seats and (b) were an awful lot closer to winning in the first place.
(Labour's defeat to the SNP is an entirely different matter, of course.)
Original post on Dreamwidth - there are comments there.