Civilization is never more than two missed meals away from collapse. In a more general sense, existential threats (or the perception thereof) erode civility and make people susceptible to tribal thinking.

We (Germany) have a number of such threats:

• Several immigration and refugee waves.
• A flagging economy due to the impeding loss of several once-reliable markets. (China lost its appetite for German cars and the States have been increasingly volatile in recent years.) The German economy is very export-oriented.
• Rising food costs due to the Ukraine war.
• COVID-19.
• The housing crisis.
• Climate change.
• The whole woke/anti-woke thing.
• An increasing perception of all established political parties as useless or even actively detrimental.
• The botched reunification. The Eastern federal countries have been disappointed by the mainstream parties so severely and continually that populists like the AfD can easily find an audience.
• A (now defunct) government coalition where one of the parties had no interest in actually cooperating with the others, the second one has a recent-ish reputation for having no idea what they're doing, and the third one is the target of a sustained attack meme campaign. Oh, and the chancellor had a corruption scandal.

Add to that the massive online presence of the hard right and you get a lot of people who stop caring about civility and start caring about simple solutions to complex problems.