It's hard to give a non-snarky answer because The Boring Company has been very light on actual details, as most of their publicity has focused on the alternative transit method they propose instead of TBM details. Even most of the details on tunneling they suggest aren't meaningful for making it faster; the only one that really is making TBMs run 24/7.

The only reason Elon thinks he can make it faster that I can divine is engineering magic.