Source: JBL gave his notice to WWE 11 months ago
According to Justin Barrasso of Sports Illustrated, JBLJBL had been planning to leave WWE for about a year due to being burnt out. WWE would usually fly Bradshaw in on Sundays so he could commentate for SDL. But the travel from his home in Bermuda had gotten to be too much. So for the last two months JBL would fly himself in on Tuesdays and just make it to the arena to commentate.
He was confronted not to long ago about this and they decided to part ways and reduce his schedule to only BIG events. Many speculated that JBL leaving was due to the bullying scandal with Mauro Ranallo. That is not the case.