To make it quick: Economics, immigration, and identity.
Economics plays a factor as europe is in a recession and is still struggling to bounce back from the pandemic. Current leader’s usually take responsibility of the economy so if its bad, most want a change in leadership
On Immigration, a lot of syrian and middle eastern refugees came to Europe and arent assimilating well apparently. A lot of europeans feel they dont respect freedom of speech, arent tolerant of religions, commit terror attacks, want to veil women etc and want their “islamic” culture accommodated at the expense of their own.
Finally identity due to, imo, a lot of europeans still relying on “looks” when it comes to identity. Europe is not as diverse compared to North and South America so large immigration of different looking groups is causing an identity crisis of sorts. People are having to ask the questions of what makes “x” person a German, Pole, Englishmen etc when dealing with multiculturalism. A lot are feeling they are losing that identity.
All these issues were there previously however, with increased migration, constant terror attacks and bad economies its making the far right messaging more appealing.