Star Trek: Picard - 17 Huge Details Everyone Missed In Trailer 2
14. Picard's Last Mission Was Unauthorised (And Went Wrong)
It turns out that Picard's standing with Starfleet is now more complex than you'd expect of a Captain whose ship is immortalised at Starfleet's HQ - he's told he has no say in Starfleet's missions, because this "isn't his house any more." Which is surprisingly disrespectful.
The reason is revealed later as it turns out that Picard undertook an unauthorised rescue mission of some sort that clearly seems to have backfired somehow. That can be the only reason this time he ignored superiors for the greater good was set apart from the others.
The suggestion throughout the trailer is that the mission went wrong. He expresses that he retired looking for safety, he walks with a cane through his vineyard and the ensign who greets him and hands him a visitors badge (itself an indication that he's lost his reverence at Starfleet) says it's "good to see you up and about again." Was he injured badly? Is that the real reason he retired?