Wilander is an anomaly. He was sort of your anti-Connors. For some reason, maybe his upbringing or something, he was a very humble man. In a short time, he wins the French Open as an unseeded player, beats some of the greatest players at the time, but then during an interview he says he was lucky to win the French, and if he plays one of the top players, he might get lucky enough to win if the other guy is having an off day. Connors and McEnroe were totally dumbfounded by this, and obviously they reacted much differently to early success.
In 88, he finally figured out that he was the best in the world, and I think he just didn't have it in him to keep it up because he knew it would be challenging. He's not like a Connors who was a brash in-your-face kind of guy who probably relished the idea of humiliating his opponents. In 91, I think Connors actually had in his mind that he could win the US Open one more time, even if he was the only guy who believed it, and it would have been all the more sweeter to do that as an old man and prove to those young guys that he was better. Wilander just doesn't have that kind of mentality.
I also think Wilander preferred to take the underdog role. He was the overwhelming favorite to beat Noah in their French Open final, in both his mind and in the minds of the fans. He came into it playing it safe so as not to mess things up, but he knows now that was the wrong thing to do. If he's the underdog, he feels he has to work harder at it and do something special in order to win. After 88, he wasn't the underdog anymore, and I think it totally messed up his motivation to win.