Because the Starmer project isn’t a party political project. It’s a catalytic project to reform the British state with a final phase of asset stripping and shedding the last vestiges of ‘liberal democracy’. The deep British establishment see the train coming down the tracks - total collapse of living standards, ecological crisis, mass displacement of people - and are building a state they think can survive it. An internally-oppressive fortress nation that models itself on a mixture of Singapore and Israel, where a sizable chunk of the population are simply surplus to requirements and a potential threat as life gets rapidly worse for the majority.

As for why individual MPs and the rest of the party go along with it, the massive post-Corbyn intake of candidates and officials were specifically selected (often against party procedure) for their “reliable loyalty” to the project. They’re corporate lower-middle managers selected because of their lack of insight, interest, or ideological concerns. Most are paid lobbyists for friendly interests and/or empty suits, promised financial reward in the form of board seats and lucrative advisory/NGO positions when they inevitably lose, whose only job is to maintain a reliable parliamentary majority for the duration of the project’s term.