Yeah, when changing the master on an ABS system you have to hook up to the ABS system electronically to bleed the system. Pretty much if you open the system before the ABS system, you going to have to get this procedure done.
It is possible that when you were working on your brakes that the loss of pressure was enough to make the already bad seals in your master completely fail. But as reminder, if you pushed the pistons on the calipers back without opening the bleeder you could have caused them to fail at that time as well. Either sorry to hear about your bad luck. So I wish you good luck
