Any particular reason Akeem left in 1990?

It seems to me they could have easily repackaged him back into One Man Gang again and gotten some use out of it him

Did Earthquakes big push essentially make him obsolete because Tenta was a better worker?

I don’t think there was any particular reason for his leaving.  He quit around the same time Rude did and then they fired a bunch of guys to cut costs anyway, so it’s doubtful that they would have bothered to keep him around. He’s another guy who could have been a challenger for Warrior had he returned to OMG after the Twin Towers breakup.