From my experience at CLPs and the like, the average Momentum member isn't very interested in the SWP. It's not the politics they want. If I were to stereotype, they're normally a young woman in her late twenties who has flirted with the Greens in the past and wants, peace, justice, and fairness. There's no real interest in seizing the means of production, etc. Their top priorities are often things like the Human Rights Act or feminist issues, for example, which the SWP is antithetical to.
Of course, that's not to say that there aren't people in Momentum interested in a similar policy overlap to the SWP, and the tragedy of Momentum is that the upper echelons are to an extent staffed by people with an interest in using their young idealist army to pursue a rather different vendetta, but I think the Parliamentary Labour Party made a mistake in the level of hostility it showed to Momentum. They're not Militant, not even especially similar. By reaching out a hand, these young idealists might have been won over, but the PLP is doing its absolute best to push these young idealists into the hands of people stuck in the early '80s.
Instead you get nonsense like this:
Which is not really an accurate characterisation of what's happening.