Twitter is a massive echo-chamber, reinforcing their belief in themselves and most people believe them because the internet-oligarchy hides and censors different outlooks on society (not that I necessarily agree with those outlooks, but still).

Best example: All of the twitter-mob was hyping themselves up about the german election, the young generation being all green, all "Generation Greta" as some called it. There was no way that anyone except the greens would get ALL the votes of ALL young or first -voters. Except reality hit and they found out that an equal percentage voted for economic liberalism and less state instead of state intervention and illiberal politics. Somehow, the calls of the left for lowering the voting age have been conspicously absent since then...