There are numerous reasons why people choose to live somewhere, and lets be honest, they will have probably been through various countries before they got to France, and eventually the UK. Why did Tommy Robinson "seek safety from his persecution" in Spain rather than France? Presumably because he thought he could do better there. Maybe he liked the weather. Maybe he liked the large expat community. Why do people choose to move to places? The evidence suggests it's predominantly due to work or family/friends.
What perhaps might be of interest, is that there have been a few studies recently into undocumented immigrants in the US, and not only do they show that they contribute far more economically than they cost, but they would also benefit the economy far more than the cost if they were involved in the covid stimulus packages doled out (which they're not currently). It's almost like people making such a huge decision to relocate are going to move heaven and earth to make it work, which benefits the host community. It's groundbreaking I know.