So we have our answer - it wasn't caused by "imperialism", but by specific laws passed by politicians, against the will of natives [1]. And we know how the economics worked out in countries that bothered to look [2].
[1] Between 1962 and 1971, as a result of popular opposition to immigration by Commonwealth citizens from Asia and Africa, the United Kingdom gradually tightened controls on immigration by British subjects from other parts of the Commonwealth. - https://en.wikipedia.org/wiki/British_Nationality_Act_1948
[1] Between 1962 and 1971, as a result of popular opposition to immigration by Commonwealth citizens from Asia and Africa, the United Kingdom gradually tightened controls on immigration by British subjects from other parts of the Commonwealth. - https://en.wikipedia.org/wiki/British_Nationality_Act_1948
[2] https://emilkirkegaard.dk/en/2024/02/fiscal-impact-of-immigr...