The question is, why do the Establishment British politicians WANT these potential voters streaming into their country?
It is a death wish, and it may be granted ever so much faster than anyone imagined.
Because the British Establishment will be obliterated by these new “immigrants” (invaders, really). Coming from all over the former British Empire, they still have their resentments against the British oppressors that held their anscestors in thrall for centuries, and old prejudices die hard. Add to that a ready-made infrastructure with at some industrial base, and that is an immense leapfrog movement into a semi-industrial world.
But, being Muslim, they will turn the British Isles into another Syria.
Same reason they want immigrants here. They get political power (votes from immigrants and sympathizers) that they would never get if conservatives were in the ascendancy.