Help! RV2 compressor blew new shaft seal

I had a shop get the AC for my 74 Duster up and running. New hoses, expansion valve, and the compressor was gone through. They flushed the original evaporator and condenser and installed new drier. Held a vacuum with no problem, then charged with 134 with the proper oil and AC was working fine. I picked up the car and drove home 5 miles, AC working ok. Shut the engine off and notice the green dye dripping on driveway. Opened hood and I am sure shaft seal is leaking as the green fluid was all over the engine bay. Now the car will be out of commision for about a week while waiting on new seal from Arizona.

My question is what do you think was the reason for the failure? Overcharged, bad seal, bad shaft?

Thanks for your help. Gary