I think the answer is manifold.
a) People fall for the “Honest Nige” persona and fall for his BS in the same way that people fell for Trump. He’s not a politician, he’s a man of the people, etc etc
b) On the face of it, many of Reform’s policies seem attractive. I am very much not a Reform voter but I believe that you shouldn’t judge by sensationalist headlines so I read their manifesto. On the face of it, a lot sounds attractive (not all, but a lot). The fact that it’s not economically viable and there are no answers on how much of it will be achieved is irrelevant. People who like Reform enough to read their manifesto will like what they read.
c) People aren’t politically engaged. They just want someone to promise them that they’ll make it all better. See point a).
d) All of the other parties are shit. The Tories are a corrupt mess, Labour is trying to appeal to everyone and letting down their core demographic in the process, and LibDems and the Greens still don’t seem to be clear what a woman is.
e) And I’m sorry but for many, yes it is immigration. Lots of people don’t know if they’re angry about refugees or immigrants, and don’t know the difference. They just know they don’t like People Not From Here. Reform put immigration front and centre. They’re not afraid to sound xenophobic or racist and that greatly appeals to those who are racist and/or xenophobic. It’s Brexit all over again.
This is their manifesto. It’s worth reading because it’s interesting what they’re claiming they’ll do. Some of it is horrifying, but a lot of it is Trump-style populist politics.
https://assets.nationbuilder.com/reformuk/pages/253/attachments/original/1718625371/Reform_UK_Our_Contract_with_You.pdf?1718625371
If you cba to read through the full manifesto, here’s their “core” promises. Immigration takes up two points out of the five, and are the first two on the list….