While you are correct - it is a stupid way to spend your money- it is his money to spend as he sees fit.
Think of the jobs this guys provided with this one act- the crane, the people who build cranes, the wall contruction crew, the intallers, etc... Not all commerce is brilliant and helps mankind, but it is still commerce.
Plus...
This is way less stupid than how the government would spend that same money. (not that you implied it should be taken from him)
Absolutely. And he might very well think the ways I would want to spend money are stupid, too. But if someday his money runs out, he may wish he hadn't spent it quite so foolishly. (It's funny how some of these very rich people don't realize that the money can be gone tomorrow, especially when one fritters it away on idiot projects like this.)