I don't think that's necessarily true. I've been on MN a long time and there was a lot more support for the Labour party 10 years ago and far fewer people talked about being a Tory voter back then. So there's been a shift.
The forum was a lot smaller then and had delusions that it had finger on the pulse of what the wider UK wanted, it wasn't helped by Justines ties by proxy to the Guardian and the prominent posters being from working class backgrounds because thier great grandfather was a miner up, despite growing up in the home counties with middle class parents.
As a whole MN has been politically on the wrong side on all major elections, those that have come good and had a multitude of gushing posts have since gone quite, see Trudeau, Macron, et al.
There was such a time that when any working class woman who was struggling complained about the benefit system not being fair to low paid workers was met with such hilarity of spamming the thread to 1000 posts about goats and big screen tv's, yet suddenly when the Tories brought in the cap of up to 26K was met with utter disdain without a hint of irony.
Any run up to an election on MN is flooded with Labour activists so much so, that any mention of any form of labour critisim is met with Tory HQ/daily mail esc hillarity.
MN is so out of touch it was a hotbed for being so pro corbyn people where unironically posting that they could never be friends with anyone who doesn't vote the same way.
MN and politics has been a hillarious decade long case study