Dale Pulde, who teamed up with M/T much later as a driver, told me that Mickey was a businessman, pure and simple. He had no allegiance to Pontiac or anything else but the almighty dollar.
If some other car company had offered Mickey more money in the late 50s-early 60s, he'd have taken their deal in a heartbeat. Just so happens Pontiac had the bigger checkbook at the time.
At least that's how I heard it.