Sure, sure, that's the great thinking of the day: billionaires can do anything they want, enter your country, become citizens, even pay reduced taxes, while rich countries (read US and UK for the time being) are closing the borders to people in real need.

So that either those people will not get at all help, or a reduced amount of countries (and maybe even poor countries) will be forced to bear the burden of helping them.

You get richer by getting trickle down economics of wealthy individuals[1], and the rest get poorer.

[1] The more plausible outcome is that, as one sibling comment mentions, you will not get that much from those wealthy individuals. They will come with their millions, squander your resources, workforce and capital, and move to the next bidder in a couple of years.