That is a hard question to answer... there are a LOT of variables that go into the performance of a video. But long story short; for whatever reason that video got a better response from an audience than your prior videos. It could be because YouTube got it right and put it in front of an audience that was more apt to enjoy it. More than likely it is because you touched on a much better combination of thumbnail design, subject matter/topic, and/or editing style.
When you get a video like this it is important to study it. See what worked and what didn't; you now need to try and reproduce those results on another video by experimenting with the things that appeared to be right about this one. Keep doing that, you overall channel performance should increase and that is how you grow a channel successfully.