I wonder if district gerrymandering plays a role in the US. When your districts become packed to the extent that it's safely owned by one party, the only risk to an elected official's seat is a primary from a more extreme candidate. So instead of finding compromise to maximize your general appeal, you would be motivated to embrace extreme ideas and promote those on TV/social media. More elected officials doing this gives license to everyone to embrace the extremes, even if they're not very popular.