I think James may be right about the deliberate misspelling of hashtags as a way of diluting them. I've never seen anything quite like the spelling variations in 'Cummings' over the past 24 hours. #CumGate #DominicCummings https://twitter.com/accessjames/status/1265025688802717698

Impossible to know who is behind this - along with the evidently non-organic spawning of the counter hashtag #ScumMedia
It could easily be channers, hyper-Tories organising off-platform, any number of the old Vote Leave digital people - or a combination of them all.

Also difficult to discern why they do it. Twitter's user base is heavily left/liberal oriented, so it massively overrepresents anti-Tory sentiment at steady state anyway.
They may be troubled by this, or disrupting it could equally just be a game to them.