Engines are complicated and the maintenance and certification requirements on such a complex system in the context of aviation is very expensive. Airplane engines must be rebuilt at set time intervals even if they’re working perfectly because of what is at stake if they fail.

Electric motors are vastly simpler devices with far less moving parts. Much less to go wrong, much less to inspect and replace.

These are savings even before you get to talk about energy efficiency.

These savings aren’t realized in the car market because if the motor of a car fails, it is just an inconvenience. All that extra work doesn’t exist.

These savings aren’t theoretical either —- there are smaller scale electric aircraft used for pilot training on the market already. An hour of time in a Cessna costs $150ish/hour, these new electric planes are boasting costs of around $30/hour.