The goal for Tesla is to accelerate transition to electric vehicles. Once that is completed Elon will move on to another project similarly to when he transitioned from X.com/Paypal to something else.

If that were true then Tesla would open its chargers for use by all brands of EV.

Teslas can charge on all other charging networks. When will Tesla reciprocate?

Tesla's mission is (from their website): "Tesla’s mission is to accelerate the world’s transition to sustainable energy."

More tunnels would be cool, but I find it hard to believe there's really that much room for improvement over established companies.

I think the hyperloop is even more ludicrous given the technological problems involved in vacuum tubes. But I think Elon realises that which is why all he did is write a memo on it rather than create a company around it.

I feel like the Boring company is what he settled on once it was made clear to him how monumentally stupid hundreds or thousands of miles of near vacuum tube would be in practice. Even if you could actually build a working prototype, it's hyper fragile and will just never be economically viable compared to other solutions.