Crazy Ranking - How many installs?

I was looking on google play and I found this game: https://play.google.com/store/apps/details?id=com.alfie.world.run.adventure
Ok, it’s a bad game… but it got 1kk downloads in less than a month… 10k in 2 days, 50k in 4 days and 100k in 5 days.

How did they made this?
How many install they have bought?

Any ideas?