The fact Mining makes previously stranded/unused/useless energy useful is not yet fully understood and far from being proper utilized.

Once you see the current possible gains made by mining as enablers for the needed capital to build the infrastructure to enclose that stranded/unused/useless energy it becomes an even more interesting topic.

It partly solves the question what will pay the miners when the coinbase becomes too low.

Well besides the fees it will be able to fund mining for a long time out.

Proper infrastructure will exist for a long time.

So if needed, since fees won't cover costs nor the public function a sound money will give and thus money will be available at sime point to cover for it since the current banking industry is way more expensive and abusive so Bitcoin will be a better/cheaper solution, that existing infrastructure in place will support it for a long time at very little costs.