I think the burn last time and the appalled membership are priced in now. Any Lib Dems who would be all that appalled by working with tories left years ago. What is left in that party is just tory economics + legalising cannabis. That'd be their path of least resistance rather than having to contend with devolution, environmentalism, etc.
Okay. But why?
the constituency I live in was 50% tory, 30% Lib Dem last time round. It would need a massive swing for the Lib Dems to win it. And if they went in to coalition with the tories you'd have to assume they'd just lose the seat back to them in the following election.
Or, supposing they don't go in to coalition with the tories you'd have to assume that my local Lib Dem MP would want to sure up their own support within the constituency ahead of the next election. Which they'd probably do by voting/acting as tory as possible to appeal to that 50%.
So the way I see it, voting Lib Dem probably gets me either: 1) a tory MP anyway. 2) a Lib Dem MP who props up a tory government. Or 3) a Lib Dem MP who roleplays a tory MP within a (probably gridlocked) coalition.