I don't think it's about Brexit anymore (has it ever been?). Yes, the vast majority in parliament don't want to leave under any circumstances, but this is really about personal agenda's and power.
Labour - Don't give a damn about Brexit, they just want to topple the Tories and will adopt any approach that they think will help achieve that - anti EU - Pro EU - anti 2nd Ref - Pro 2nd Ref - Pro election - anti election. They swap around depending on which way they think the wind is blowing.
Lib-Dems - Their approach was dictated by their devastating result in the 2015 GE. Adopting a clear policy that they knew would make them appeal to the 48% who voted remain gave the potential for them to recover a lot of lost support. They knew they would never appeal to the other 52% but when you're recovering from rock bottom that doesn't matter, it's still a huge step back to potential political credibility. It was a clever strategy which has worked, but like Labour it wasn't driven by a desire to to do what's best for the country, it was to do what's best for the party.
SNP - A one trick pony - Scottish independence. Their sole agenda in parliament is to disrupt the the running of the UK that they don't want to be a part of.
DUP - They want to ensure that nothing interferes with or undermines NI's place in the UK (understandably). Nonetheless, it's still driven by their personal agenda, not the UK's.
Conservatives - Couldn't contain the internal splits on Europe any longer, compounded by May's government trying to be too clever by wasting years pretending to deliver Brexit whilst not really trying and hoping the problem would go away, while Johnson, Gove and their ilk sniffed an opportunity for the top job (who knows what their actual view on Brexit is).
And now they're scared to go back to the electorate. They're not fit for purpose.