[morei]

How is this better than an electric motor turning a fan?

Modern high-bypass jet engines get the vast majority of their thrust from turning a fan. The turbine part is (mostly) just used to generate torque to drive the fan.

Modern electric motors also have ridiculously high efficiencies (> 97% isn't uncommon).

So how would using electricity to heat the air be better than using the same electricity to turn a fan? The only place I can think of is high supersonic where fan efficiency starts to drop.