Wouldn't corporate tax also be another moat to prevent other businesses from reaching Amazon's scale?

And isn't Bezos trying to rub shoulders with politicians?

Possibly. But that also depends on how corporate taxes are implemented.

I have no clue what his aspirations are, I don't follow this type of news very much at all, I just remembered that he stepped down and now suddenly he thinks companies should pay more (or in Amazon's case, some) tax.

I expect a huge amount of his net worth is tied up in Amazon, so Amazon is still very much his problem.

I think he fears more that Amazon (or other big tech companies) are smashed into smaller entities.