As I suspected, Corbyn never stopped wanting Leave, but had to pacify his PLP by paying lip service to Remain.
Remember how he immediately rejected the idea of Ref# 2 and said we must accept Brexit.
The Guardian reported that the Shadow Cabinet have rumbled this and they decided he had to go now - not just because they think he can't win an election, but because they know under his leadership that Brexit would be in their manifesto, official Labour policy.
The Shadow Cabinet hope to install a Remain leader, who'd campaign instead for Remain if the new Tory PM calls a snap election.
If Labour then win a majority, maybe in alliance with the SNP, they have a mandate for Remain and the referendum is null & void.
Reports in a few papers, e.g. Guardian :
"Jeremy Corbyn has been accused of trying to consistently “weaken and sabotage” Labour’s campaign to keep Britain inside the EU"
"Wilson said the “greatest betrayal and final straw” for him and many colleagues was evidence handed over by “unimpeachably neutral Labour in [for Britain] staff” that Corbyn’s office – “for which he must take full responsibility, consistently attempted to weaken and sabotage the Labour remain campaign. For example, they resisted all polling and focus group evidence on message and tone, raised no campaign finance, failed to engage with the campaign delivery and deliberately weakened and damaged the argument Labour sought to make.”
This helps explain why Labour Remain didn't mobilise sufficient labour voters: deliberate sabotage from the top
Corbyn & Milne belong to a tiny segment of Labour that thinks the country must hit rock bottom and descend into chaos before the population would accept truly radical policies. New Statesman
Collateral damage getting there doesn't matter. So they are for Lexit.