Units are issued warning orders to prepare for deployment months before actual deployment orders are issued, he knew his unit was preparing to deploy. It's a nice little play on their part to get people to say "well hell he didn't even know, the orders weren't issued". He accepted his appointment to the SGTM academy and was frocked to E-9 knowing his unit was going oversees. THEN he quit the course and chose to retire after he explored his options to run for congress and found out he had a shot. Sorry but I have a problem with senior leadership bailing out when it's time to go and that is not denigrating his service, that is criticizing his decisions.
Now if he would have turned down the course and promotion to start with because he wanted to run for congress I would have no problem with his actions. Once you are eligible to retire nobody should be criticized for doing so but this guy reenlisted and accepted a position knowing they were going to deploy and then said "ah nope not me".