I don’t think he is/was part of the team. He was a useful idiot.I actually think that you are missing a key tenet of Corbyn's approach. You seem to imagine that he jumps on each new madcap bandwagon as it comes along by chance, then champions its cause in the parlours of Islington, because he's a bit dippy. I believe it is far more pernicious than that. My own thought is that he has his people out spotting disruptive causes with potential so that they can be exploited for their diversionary value in the great struggle. There are desired qualities, such as upsetting the status quo, but there are those that are essential, such as causing division and stoking hatred.
Corbyn's job in all this is to provide protection for the internationalist cause by providing bandwidth-consuming distraction while the real work is being done elsewhere. He knows all too well that groups like Antifa, SWP, Momentum and CPGB are more than capable of operating effectively in the shadows (Hijacking seemingly 'woke' and 'worthy' causes for their own agenda) while he keeps the public gaze fixed on the public face of domestic arguments.
Corbyn is part of a huge international team, not the leader or agenda setter.