I don't think it's being suggested that a pay-for-review scheme was what caused it to be a hit.

The game was available on the store for seven months without getting much traction. The developer probably thought he would try some kind of pay-per-review/promotion service to get a few more downloads.

This got the game into the charts, but it only really began to take off because unlike many of its peers using pay-per-review the game actually had a hook that got people playing. In this case the pay-per-review was a tiny catalyst for vast growth.

Of course, this assumes the developer used some sort of paid promotion service.