"High leg" means absolutely nothing with regard to the phase-to phase voltage, so if feeding a single phase 230V rated motor, it can ONLY be phase to phase. You CANNOT get anything higher than that. So unless someone bought a 200V rated motor, what he said is just their attempt to avoid having to eat a bad motor. Even if it was a 200V motor and you gave it 250V, it would take a long time for the extra heating effect to damage the insulation, in fact people do that sort of thing all the time (in emergencies) with machines like compressors that cycle on and off because they often don't run for long enough periods without rest to cause immediate thermal damage.
But was it perhaps a 3 phase motor and you assumed it was single phase? Connecting a 3 phase motor with one phase to ground would cause some damage. But against, immediately? I would not think so. The motor would try to run single phase but would not spin, so current would rise fast and trip a breaker or clear a fuse.
Bottom line, if you connected it correctly and it was the right motor, it was bad. And given that it fried instantly, I'd bet big money it was bad before you got it.
