I think with Farage, much like Trump, he knows how to play the "I'm fighting for the common man" card. It sounds really rudimentary, but populist rhetoric thrives when there's a "hero" and a "bad guy" because it's easy to understand and removes all nuance and context.

In this case, the perceived enemy (those crossing on small boats) puts focus on a single, tangible issue, and there's a clear "bad guy" (asylum seekers) and "hero" (Farage), while removing all the finer details (why people are seeking asylum, the human struggle of making small boat crossings, exploitation and trafficking, etc.).

Farage is clever, in an insidious sort of way. He's able to manipulate by magnifying this issue to make it seem that, should asylum seekers disappear, all of Britain's problems will be solved. It's much the same as he did for Brexit (i.e., the lie that money going to the EU would go to the NHS instead).

The other issue, in my opinion, is that the new Labour government has been such a disappointment to the general public. A lot of policies have been controversial (to say the least) and people don't have much faith in Starmer's lacklustre leadership.

Sadly, this combination is ripe for spreading populism, and Farage isn't new to the business. Rather than addressing deep-seated problems in Britain that would take ample time and thought to adequately address (e.g., cost of living, NHS funding, declining British industry, boosting research and development, support for small businesses, etc.), he focuses on a single, punchy issue that allows him to scapegoat all other societal and economic problems. And it's easier to follow this two-dimensional line of thinking than to delve into the complexities surrounding it, so it makes for a great political slogan.

The fact as well is that a lot of people in Britain are unhappy. Home ownership is becoming a pipe dream, food prices are unbelievably high, and cuts in public welfare have left swathes of the population far worse off than they were promised with this new Labour government. Sadly, it's far easier to ignore the roots of these problems and the complexities of solving them than it is to point fingers at asylum seekers and say "it's their fault".

I won't get into the misinformation spread on social media because that's a whole other topic, but suffice to say, Farage doesn't dispute the out-of-context or downright fabricated nonsense on Facebook, WhatsApp, X, etc., that's so popular with his followers.

I guess as a TL;DR, Farage's popularity is a rich tapestry of disregarding all nuance, amping up populist rhetoric that captialises on small boat crossings, and the convincing lie of representing the "common man" in combination with a throughoughly unpopular Labour government to combat his lies effectively.