- One person on the team does not respect him. That is pretty unambiguous.
- His manager puts his own (in all likelihood, based on quite limited information) opinion about the one guy over the opinion of the team lead. The team lead definitely knows the guy better, yet his manager disregards that. Why would he do that if he believed that the team lead was doing good leadership? Questioning the behavior of your subordinates is something you do when you don't trust in their abilities.
- The post mortem. If you are the team lead and you want a post mortem, then you will do a post mortem. "Because I say so", should be enough of a reason. Yet somehow his own manager needed to get involved, to force through the decision of the team lead? This also relates to the point before this.
- The Team. And I think this is the biggest tell. Imagine you are a team lead and you tell 10 people "we are doing X", one guy disagrees. There are still 9 other people, if they trusted the team lead as a leader, they would take his side, especially if X is something as obvious as doing a post mortem. This whole situation can only develop if the 9 people "who like to work with him" refuse to stand up for him at all. If you as a leader have 90% of the people behind you everything you say will be done.
The real question is why the rest of the team is doing nothing. Either it is because they are more afraid to go against the one guy (unlikely) or because they do not think it is worth it to stand up for the team lead. The real thing OP should consider is why his team does not appear to care the tiniest bit about his leadership position. If they did, the one guy would not be a problem at all.
One question remains, why do they love working with him. I do not think they are flattering him, I think they mean it. Often working for a weak leader is easy, because you can set your own rules and you can push your leader around. They probably enjoy that the atmosphere in the team is more relaxed, they get to have more influence on decisions and they can deflect work they do not want to do.
- One person on the team does not respect him. That is pretty unambiguous.
- His manager puts his own (in all likelihood, based on quite limited information) opinion about the one guy over the opinion of the team lead. The team lead definitely knows the guy better, yet his manager disregards that. Why would he do that if he believed that the team lead was doing good leadership? Questioning the behavior of your subordinates is something you do when you don't trust in their abilities.
- The post mortem. If you are the team lead and you want a post mortem, then you will do a post mortem. "Because I say so", should be enough of a reason. Yet somehow his own manager needed to get involved, to force through the decision of the team lead? This also relates to the point before this.
- The Team. And I think this is the biggest tell. Imagine you are a team lead and you tell 10 people "we are doing X", one guy disagrees. There are still 9 other people, if they trusted the team lead as a leader, they would take his side, especially if X is something as obvious as doing a post mortem. This whole situation can only develop if the 9 people "who like to work with him" refuse to stand up for him at all. If you as a leader have 90% of the people behind you everything you say will be done.
The real question is why the rest of the team is doing nothing. Either it is because they are more afraid to go against the one guy (unlikely) or because they do not think it is worth it to stand up for the team lead. The real thing OP should consider is why his team does not appear to care the tiniest bit about his leadership position. If they did, the one guy would not be a problem at all.
One question remains, why do they love working with him. I do not think they are flattering him, I think they mean it. Often working for a weak leader is easy, because you can set your own rules and you can push your leader around. They probably enjoy that the atmosphere in the team is more relaxed, they get to have more influence on decisions and they can deflect work they do not want to do.