Whether the people are partially to blame or not is a complicated topic. Both in the US and Italy, about half of the population were educated/smart enough to see through their propaganda. The right wing party still won though because they picked their target audience effectively and tailored their whole campaign around that audience.
No, the Desktop Environment (KDE, DE stands for Desktop Environment).
Kubuntu is a separate thing, it’s Ubuntu with KDE preinstalled.
KDE Neon on the other hand, is an ubuntu based distro from what I understand, I’ve never used it though.