Neither side truly want a election: 1. They don't want the blame for Brexit to be placed at their feet; 2. They both aren't wholly confident they could win on their terms (read: need a coalition); 3. They know Brexit is going to be terrible, and frankly they just want to push enough buttons for someone else to do something about it and make it go away. The Lib Dems have lined themselves up perfectly to revoke A50, and take the blame. Such an act may damage their party further in the eyes of the Leavers, and also some Remainers (some are conflicted over misinterpretations of 'democracy' and 'will of the people').