How come? Mainstream parties are openly ignoring one of the main concerns of a big block of voters. Then some parties start catering for that concern. That’s pure democracy feedback loop in action.
Maybe you don't talk to rightoids enough. They get braver every day. Things they wouldn't openly say 10 years ago are said in the open now. Just pausing immigration will do nothing. Some of them want blood and to ruin a large group of people. Others don't "want" this, but will do nothing if it happens.
Maybe some of „good“ parties should start playing this democracy game and address some worries of the people? Mainstream parties are destroying democracy by ignoring the voters. Or flat-out lying by pretending they do address those worries and then doing 180 right after the elections. E.g. what CDU/CSU did in Germany. I wonder why AFD is doing so well...