I think mark (inadvertently) flags an important factor, which SkStu mentioned earlier - social media. It's probably worthy of its own thread tbh (cos this post is going to veer off-topic...)
It's clearly not the only factor of course - the abortion referendum in 83 was fairly fractious and there was no social media then. Abortion is pretty much always going to be an emotive subject.
But social media does seem to be able to have a big impact on people's views (as mark has shown) I can't remember where I read this, but there was a survey of maybe 100 people attending a flat earth induction (or something like that) and every one of them got their interest in flat earth from YouTube. There was a
study last year which said covid denial/anti-vax views could be linked to 12 influential people through social media. There's an
article on Forbes about the link between social media and misinformation too. And National Geographic ran a feature a while back on what it called an attack on science, along the same lines.
It feels like these sort of nutty things - you can add in climate change denial, using your pronouns, alternative medicine, and so on - have been growing in recent years, whereas you would like to have thought increased information would decrease their prevalence instead. Some are harmless as they're clearly stupid (flat earth); others are potentially very dangerous (covid denial/anti-vax)
On a related note, I got the 50th anniversary Apollo 11 boxset there a couple of years ago and one thing it includes is a BBC debate from shortly after on the philosophical and social implications for mankind arising from travelling to another world. It's amazing how respectful the debate is, and how much it benefits from that (albeit it's a social debate rather than a political one, so it'll always be less charged)
Or you can take the infamous
Life of Brian debate in 1979 between John Cleese, Michael Palin, Malcolm Muggeridge and the Bishop of Southwark - the latter two argue in a more "modern style" (for want of a better word - personal attacks without making any real valid points - while the Pythons (and moderator Tim Rice) try engage in a genuine discussion. It's notable that the audience sees this almost straight away and sides with the Pythons. There's a very good
background article on Wikipedia about the debate - for example "Cleese said [in 2013] that it left him bored and he realised that there was no attempt at a proper discussion, and no attempt to find any common ground."
I don't watch a huge amount of TV debates (or TV in general), but I don't think debates these days come close to this standard very often. I do think social media - 140 characters, block who you don't like, dismiss people as racist/right-wing/liberals/transphobes/TERFs instead of making a point, and so on - really does play into that.
And if that's the case, this sort of stuff is only going to grow in the coming years unfortunately, and not just in the US.
As I say, it can't be the only factor, but I think it is a big one.