Permanent magnet motors are simpler and cheaper to make, at least in the small (yes, small --- there are electric motors in the MW range in industrial applications, which are themselves larger than an average car) sizes found in EVs.

AC motors are not magic. The core is essentially just a coil with one turn, so it can generate only a very limited magnetic field. So they have to be bulkier for a given power density and generally slightly less efficient.