Corbyn's rallies in September in the run up to a leadership election can in no way be considered the same as those now being held by Trump after he has won and is 4 years before any further election.
I agree there is a big difference between having a rally during and after a campaign.
My point was that some UK leaders do have rallies, and, as with the PLP, the Republican party leadership don't have much room to manoeuvre if Trump still has popular support. If the PLP started to threaten Corbyn and Corbyn could still draw on popular support, I suspect the rallies would start again.
Do you really think Cameron and Theresa wouldn't have given their right leg to have crowds like that turn up to their pre-election speeches and meetings?
Corbyn won the leadership battle, but May is PM with very little opposition. I honestly think she is relieved that she doesn't have to do rallies. I suspect Boris would love a good rally though!