I believe he got into a physical situation with his wife while "under the influence".
They notified him he was fired from the tour by fax. Quite a classy operation. When I was going to school in FLA, Greg Allman played in every dive bar in Daytona. A friend was visiting from New England, so I thought I'd take him to one of the shows. My friend couldn't hear the vocals very well, so he asked a roadie to turn up Greg's mic. 5 minutes later the show was stopped after 3 songs because Greg's throat was sore... no refund. So what if you can't sing ? Do a blues instrumental for 40+ minutes !!!! What an arse.
No way would I pay to see the Bros with just him and Butch Trucks as the only originals.