I would bet that it's more than just weight, aero, and battery tech. From squeezing every bit of efficiency out of the motors, to mundane things like the HVAC and infotainment systems.
Since it's a small team, they may have looked at 2 speed transmissions. Both ZF and Getrag make them.
Here is an article on a startup that makes them, too:
Startup Says its Two-Speed EV Gearbox Is More Efficient Than Single-Speed (interestingengineering.com)