My reading is that there also is no single cause here - say Israel. There is a coalition of people concerned with 'pre-emptive defence' of Israeli interests who think they can do this via a mix of publicising claims of anti-semitism and real semitism and linking them to the leadership centre and then a group of PLP and labour party staff and members who ideologically oppose what Corbyn means for the party, the party that they by and large signed up for and committed to at a time when the left was pretty much a dead force in the party, or who they played a leading role in defeating in the party - and they're happy to go along with the former, but defence or furtherance of Israeli state interests doesn't play a central role in their thinking or actions beyond generic right to exist stuff.
The only ones who think it's solely about Israel are, imo, the loons and their mirror image on the other side - but that seems to have tempted those opposed primarily (or solely) to the latter anti-left stuff into a coalition of their own that centres on defending the loons as reflex - the old trot sectarian defence of the indefensible and the blind-eyeing of stuff that they think they need to keep quiet about for wider interests. See RESPECT, see ongoing stalinism as regards syria and other places. It's like all the criticisms of campism from these traditions have gone into reverse and it's pick a side time, prods chest, pick a side.
Yep, part of this is kind of what I was trying to say in cyber-security speak earlier.
A range of people and groups are making the actual accusations, feeding stories to sympathetic media, running trolling campaigns from both sides of the fence etc.
Different actors are doing this for different reasons, and have access to different kinds of capabilities (e.g. front groups, 'legit' groups, media outlets, disgruntled ex-party functionaries, botnets, fake personas, forums and/or lists where they can mobilise a swarm of people for a particular action)
If something one group is doing is obviously working though, e.g. producing exploitable angrily defensive behaviour, or foot in mouth responses from Labour left figures and/or supporters say, then there's a tendency for other actors to pile on, to adopt and amplify the attack, often causing a further exploitable meltdown and so on.
Separately, there are several groups, your 'coalitions' of pro-Israel and right wing Labour, and I would also argue broader capitalist interests, who are trying to exploit (and may to some degree sponsor) those accusations, media events, trolling campaigns etc.
So for instance, I find it highly unlikely that the neonazis trolling Luciana Berger were a 'Mossad false flag operation', that's loonspud talk. It's much more likely they were actual NA edgelords doing the sort of stuff that those pin-heads like to do.
But the coalitions of interests who exploited their action by consistently attributing all the antisemitc abuse directed at Berger to 'Corbynites', until for many people that became the reality, may well have been motivated by e.g. 'pre-emptive defence of Israel' and/or shifting Labour to the right etc.