Their new support staff is supposed to be pretty good, and they not only got very good players for their positions (needed 2 NA players), they got basically the stars of the teams the players came from.

Keep in mind that the upgrades TSM made were vast upgrades as well. They have the most potential benefit because every member aside from Bjergsen had become pretty bad even by NA standards.

Also, TSM had historically been well enough off that they could get early leads even against great teams, but even if it was a 5K gold lead they would still find a way to throw it.

The reason for this was of course their poor shot calling, that had caused even their star player (burdened with shot calling) to diminish mechanically as he had to focus more on distractions that he wasn't particularly good at to begin with.

TSM picked up someone widely regarded as a top two western shot caller and world class shot caller. Alongside their new staff, this should completely shore up their shot calling/macro issues as long as something seriously wrong doesn't happen.

We don't know if TSM can function as a 5 man roster yet, some teams don't click...but TSM certainly did very well in the off season and it can be argued they made the best improvements.

You also have to take into account that Yellowstar might have a big enough impact (bringing world class in game shot calling to TSM), than simply upping your mechanical stock a bit.

Forgiven is better than Doublelift but they're both somewhat similar in style, and just very good mechanical ADCS (though Forgiven is a probably a little smarter when it comes to the game), and Doublelift is already very good, to the point where if you had Forgiven over him in your team, it might not see a huge amount of difference.

Bit wall-of-texty, but I hope this explains to you why people think TSM did well, or perhaps the best, in the off season. Regardless of whether or not you agree with it.