Loose Connector?
A loose or badly crimped connector to a stepper can cause high voltage spike to kill the stepper driver, then the shorted driver cooks the motor.
Unplugging drives live is a no-no, and loose conectors are a hidden version.
Use GOOD QUALITY plugs, hopefully with crimped, not soldered wires.
Mechanically support wires near terminations.
Use the expensive fuses. Mightn't save the driver, but helps decrease the smoke at higher voltages. Low current arcs less than even 2A can be spectacular.
Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.