I agree that the British system was very much a very well controlled caste system until about WW1, but this is a wild take. Yes, poor ppl left England because there was a hope of something better or different elsewhere, but that doesn't negate the fact that the 'better" was stolen from others
And I'm saying this as someone whose ancestors were, quite possibly, some of those who stole & killed. If not, they definitely benefited directly from that stealing & killing as they have been in North America since the early 1700s at least.