Why does the Instagram algorithm push some small accounts to viral?

[boostbysocial]

One who posts in the same niche as another and one who posts two posts a day, one explodes and the other remains with 300 followers. One whose niche is the same as another, and one who posts two posts a day, one explodes, and the other posts 300 followers. I have been using ig tools to try to get some clues to the content pattern and then comparing it to a few other content patterns, but I can't figure it out. Is there any evidence that the algorithm has been boosted by social engagement management, in particular boostbysocial or similar services, and that this has contributed to their success?