I think he means the worst team of all teams to have won a major - Like in terms of the lineup and what happened afterwards with the team!
So he put Gambit on the 1st spot because nothing really great happened to their team after they won the major - Yes they got 3rd/4th place at DreamHack Masters Malmö 2017, but nothing great in particular.
I think he put C9 on the 2nd spot, because nothing happened to the team as well after the major win - Everyone had high expectations for them after winning it over FaZe - Kinda like Gambit - Also, you gotta add in that Stewie left the team a month or two later after the win, and I think turned the tables for C9 throughout the whole year.
And I think put EnVyUs on the 3rd spot, because the team literally went out of groups at MLG Columbus 2016 after they won their first major at Dreamhack Open: Cluj Napoca 2015. Nothing great happened to EnVyUs either, only a bunch of roster changes which ended up being a really bad idea.