They might have oversold him alcohol. It might be with 10 flight attendants onboard he received drinks from different crew members and shifts. It’s also possible he brought alcohol onboard and consumed it. He might have stolen mini’s from the galley. He might have had his girlfriend order for him. The final choice and most likely is he combined alcohol with drugs. The warning on many drugs not to take with alcohol is 99% ignored. Ambien and alcohol costs the airlines millions in diverts.