The practical reason is that people are extremely agitated and even if they're a fraction of the country that's still enough people for civil conflict. I think you're being a little dismissive of the fact that people are emotionally engaged and FAANG taking down parler is not only further agitating angry people but drawing more people, especially those of whom who hate and distrust "big tech", into the political divide. This isn't a knock against their decision to decouple themselves from parler, but just an observation that these actions are making people angrier than they already were. When you have two spouses who hate each others' guts and haven't been able to stand each other for years, with no improvement in sight, divorce is probably the right decision.

I think the lies and conspiracies are just a manifestation or side effect of the social and political divide. Its like imagining someone you already hate. "They're plotting against me", "they're going to get me", "they probably spilled that milk on purpose to piss me off", etc. And I think there is some substance to the hate, not to the conspiracy, but I see that our society has gotten to this point for real reasons and disagreements that can't be compromised on

edit: typos