Many people got a shoutout from pewdiepie, many who got a much bigger shoutout than Jack got (pewds basically said he liked his accent and "top of the morning" and that was about it) many other channels had much bigger shoutouts and did nothing with it. I think Jack said he got a few thousand subscribers from it, which at the time would have been massive for him, but he mentioned that it had no lasting impact.Don't forget that Jacksepticeye got a huge shoutout from pewdiepie, there's no saying what could have happened to his channel if he didn't go viral like that.
There are people who are associated with big Youtubers and it still takes them years to get big. Look at Markiplier's group, Lordminion777 hasn't hit 2 million subs yet and has been doing it for a decade. I know a gaming channel that has 11K subs despite having more than 200 videos over the course of 11 years.
Even if a channel is steadily growing, it can take 5 years or more to get to the point where they are moderatley sized, but even longer to be big, unless they do something viral.
Even pewds mentioned that in a stream with him more recently, I think with their bottle flip collab, that jack worked long and hard for it while many others feel off the face of the planet.
Lordminion unfortunatly isn't that exciting to me. And my point is mostly just to have patience. people are hoping for the million subs in a month which just isn't going to happen. You might not even get a million subs in 10 years. It's a long game.