Lets explain the logic.
Assume you have 10 million dollars invested, which is invested in various items but gives a (pretty high) average return of 10%
So your yearly income is 1 million.
Except its not, because most everyone has some debts and there are always taxes.
So for simplicities sake you have a 20% tax rate because your investments are split between long term and short term, dropping your income to 800k.
So your actually received income is 800k
Now your accounant comes to you and says "they have changed the law, your income next year will be taxed at 45%, meaning your expected income after taxes is now 550K, the only way around it is to give up your citizenship and leave the country, you could become a singapore citizen and your tax rate will drop to 0%"
So, to simplify it.
Nation A
550k per year income
Nation B
1 million per year income
Why would you choose nation A again?