You need to contextualise his actions in the understanding that he's an intelligence plant that successfully avoided the UK getting an anti-imperialist leader right before the Ukraine and Palestine kicked off. We could have had Corbyn or Rebecca for all of the current events, the UK would be the spearhead of antizionism and it's very possible that splits in the west over the Ukraine war could have occurred.
What they cared about was keeping out the left and avoiding harm to the imperialist projects which must have already been in the pipeline at the time. This behaviour has not stopped. It's everything to them.
The Labour party dying doesn't matter to the intelligence apparatus as long as it maintains these projects. They will get Reform next and they know imperialism is perfectly safe in their hands.
If a new left rises up they will handle it separately as and when the time comes. The immediate battle is what they care about.