It's not possible to become a billionaire without mass exploitation.

Nobody "earns" a billion dollars.

And even if, by the most bizarre set of circumstances, you manage to do it?

It takes a skewed moral compass to have the resources to end mass poverty, and choose not to.

Let's say I suddenly had $10,000,000 and lived off that, and earned no interest, and earned no further income for the rest of my life.

Let's say I live to be 100.

That's still $166,666 per year, which is quite a lot of money to live off of.

I can very very easily live off $10,000,000 with no interest for the rest of my life.

So it should be obvious that keeping anything above that amount is completely immoral.

Extreme wealth is always immoral.