That just says Musk is a good company salesman. Speaking of which, I can't find news about this funding round (found it; turns out there is a lot of dumb money out there). Plus Musk is famous for shady company operations (SolarCity being acquired by Tesla at an inflated price to pay off his family).
Last I read about them their tunnel boring tech wasn't revolutionary, it was just smaller diameter tunnels.
Typically, tunneling involves abandoning the tunneling machine underground because it's too difficult and expensive to retrieve. The Boring Company's innovation was to find a way to retrieve the machine inexpensively, thus significantly reducing the cost of tunneling.
They also operate the machines remotely, so that humans are not risking their lives underground.
Tunnels are a good thing. They cut across a city without paving over more greenery. They will reduce surface traffic.
Last I read about them their tunnel boring tech wasn't revolutionary, it was just smaller diameter tunnels.