Keane said that it was suggestive of contemporary players’ behaviour, whom he says are”very weak human beings”.
Mourinho was sacked on Tuesday, using former striker Ole Gunnar Solskjaer appointed caretaker director until the close of the summer growing season.
“You’d fall out with those players,” Keane told BBC Radio 5 live.
“players that become fat, do not train properly and are not producing… For some to down applications, shame on some of those players.
“I’m not Jose’s greatest fan, but I can not bear footballers who hide behind agents, their pals from the press – it’s a tiny joke.”
Mourinho was sacked after two and a half a year in control, together with United 19 points behind premierleague leaders Liverpool.
He was reported to have fallen out with players, including record £89m signing Paul Pogba.
Former Republic of Ireland midfielder Keane added: “The players got away with murder. They hide behind the manager. They have chucked him under the bus.”
‘It’s not old school, it’s Great college’
The 47-year-old said:”I was somewhat old school. But I would call it not old school, but good school.
“Anything has gone on at the bar, whenever you move to the pitch – particularly at a large team like United – you move outside and give your all, no explanations.
“This notion why these players are upset… It’s isn’t only United, however the player. They are not just weak players, but have become weak individual beings. You cannot say a word to them.
“Players are not easy to hide behind societal networking, their cars and their girlfriends, the entire lot.
“I was very blessed with the dressing room I was in. You will find good men, great leaders and characters, but that is in shortage in the game today.
“It would not have happened within our dressing room. We would not have tolerated lads not setting a shift “