Honestly, I don't think it was the Brexit vote that was to blame; exactly the same (in fact, probably even worse) has happened in America, and that excuse doesn't exist here.
I'm more inclined to point the finger at social media, which has led us into this post-truth age where the majority now just lives in their own political bubble, bombarded with stories that amplify their natural viewpoints and vilify anything or anyone that's contrary to that. What's true or rational or pragmatic takes a back seat now to whatever is most likely to beat the other side, and own the libs/fascists.
If I was emperor of the world, I would force everyone to spend equal amounts of time reading media that is contrary to their natural prejudices. Want to spend 30 minutes reading the Telegraph online? That's cool - but now you've got to spend 30 minutes reading the Guardian as well before you log off. Want to watch GB News before you go to bed? That's cool, but here's your copy of the Socialist Worker, and there's going to be a test in the morning. And vice versa!
I think you're about 90% correct.
My only argument against social media being the main cause of division would be, haven't we been very divided like this before in the 1980's before social media existed?
I didn't live through the 1980s but from the documentaries it seems like it was a very divided and angry time in British politics, maybe even close to what we are seeing today?
I'd also say there was something almost unique about the way Brexit tore the public apart. I think it's when political debate took a really dangerous moralistic turn (and I say that as someone who supports Brexit and wanted the referendum)
It felt like the major issue it was fought on became immigration. We had the democratic deficit argument in there, self-determination yes, but immigration dominated on both sides of the argument.
Remain were overwhelmingly favourites to win. Even on the day of the vote leave was something like 10/1. Then the result comes in and it's leave. Suddenly there's a reckoning. Are 52% of the country racist and intolerant?
Are people who think differently to me actively evil? Is Farage literally hitler? If Farage is Hitler surely I'm morally obligated to hate his supporters.
Meanwhile leave voters get riled up by talks of Russian interference and a second referendum.
Two tribes emerge.
Then there's the Black Lives Matter movement where footballers are suddenly taking the knee and race is at the forefront of the news. One side thinks it's being forced on them and the other thinks it's all fair game. Generally leave voters (often white working class) are sceptic of the movement and remain voters back it.
Which leads us into COVID. Generally speaking remain voters back vaccines and lockdowns and leave voters are sceptical of vaccines and lockdowns. This again falls into the trope of... Is the other side actually evil?
One side things they're being locked up against there will and having things forced open them, one side thinks people against lockdowns and vaccines are essentially responsible for deaths.
Add to that Trumps second term and the US split even more extremely than the UK and you have a recipe for absolute mistrust, anger and division.
Since Brexit it's felt like one thing after another is two tribes where it's more than just "the other side are wrong" it's "the other side are evil"
But where I think you are right is social media has exacerbated things massively.
1. Clips. Short form clips do really well on social media. If someone goes on question time they're looking to get in a killer quote or opposition put-down that will go viral on social media.
2. Constant access/ echo chambers. Say you're of the opinion trump is literally hitler, you can access supporting evidence 24/7 of ICE deportations, people saying slurs, a constant steam of confirmation bias.
Say you think illegal immigration is too high. You can access story after story of illegal immigrants doing bad things. Confirming your world view even more.
This adds to the sense the other side is ideologically evil.
I think the combination of post-Brexit tribalism and social media has made political "debate" shows just utterly pointless. How many people who watch question time are not sure who they will vote for in the next election? I bet it's very few.
People just want to see the people they agree with eviscerate their political enemies.
I think most really politically interested/active people have made their minds up by the time they're an adult. The results of elections are probably decided not by those of us who watch political shows and talk politics on X and internet forums, but by people who avoid all of it.