Former manager Kinnear was a controversial appointment in June and announced his own arrival in a radio interview during which he claimed he was more intelligent than the fans and got several of the players' names wrong.
After being eventually confirmed as director of football, Kinnear managed to sign just two players in two transfer windows, securing forwards Loic Remy and Luuk de Jong on loan.
The departure of influential midfielder Yohan Cabaye to Paris St Germain last week was met by an angry reaction from fans who then saw the club fail to replace him on transfer deadline day and fall to a 3-0 home defeat to local rivals Sunderland just hours later.
The club have now confirmed that Kinnear has left his role and Shearer, who replaced the 67-year-old as manger after he was forced to stand down due to ill-health in 2009, believes a combination of all those factors could well have led to the former Wimbledon manager's resignation.
"The life at Newcastle United," he told BBC Radio Five Live.
"I shouldn't say I'm surprised but I was surprised in the first place when he was announced director, particularly the way the news was broken when Joe himself announced it on the radio when he got some of the players' names wrong.
"What has he been there now, about seven months? And two players have come in, albeit both players on loan.
"Maybe it's Newcastle's way of trying to say that the performance on Saturday wasn't good enough and why they didn't get any new players in, maybe that's one of the reasons.
"But they can only get players in if there's one man prepared to sign a chequebook."
He added: "You just never know what goes on at Newcastle behind closed doors.
"I think we were all surprised because Joe had been out of football for so long. Let's say that we hope he's okay and it's nothing to do with ill-health but it's just bizarre sometimes at Newcastle.
"Four, five weeks ago Newcastle were going so well, still in the FA Cup, Alan Pardew was getting manager of the month awards (and) they were looking up the league rather than finishing in mid-table.
"It's amazing what happens in three or four weeks in football, 3-0 on Saturday hurt everyone and they were second best all over the park on Saturday with a lack of fight and a lack of desire from the players and now it's come to this."