According to James Forsyth:
Khalid Mahmood has resigned from the Labour front bench saying that 'A London-based bourgeoisie, with the support of brigades of woke social media warriors, has effectively captured the party' source
This comes after the historic election loss for Labour in local elections, where the party bled even more in working-class areas than it did in 2019.
He probably believed that it could be wrestled back from them once Corbyn was kicked out. But it's now clear that that isn't going to happen any time soon.
The party is basicaly dead outside the M25 and a thin sliver of the most urbanised areas of the north.