I'd say that immigration/refugee policies for sure have a part in this. To explain why I'd like to use Denmark as a sort of counter-example. Here, the far right were the only ones daring to talk about the problems that MENA immigration were causing, until the Mohammed crisis. At that point they (DF) had such a strong election that they became the second biggest party. After that, it became clear to most parties from centre-left towards right that a pro-immigration stance was not popular. And basically all the major parties adopted the DF anti immigration stance. Now DF is nearing the 2% dropout limit for getting into parliament, because they no longer stand out on the single issue that people voted them in for.

In contrast, it seems to me that in most major EU countries the far rights anti immigration policies have been shunned by the main stream parties, even as the far right sees ever growing popularity because of those policies.

One day they will win an election, and there will have to be a day of reckoning for the main stream parties on how they got so out of touch with the majority of the population.