Psyonix market personnel are specifically selected to launch the Rocket League in the summer of 2015 because of less competition Rocket League Items. At that time the media did not have much content to write, the host can choose the game is also few, Psyonix thus got a lot of free media exposure opportunity.
At that time PS4 game library is still relatively thin, so every time the release of the game is a news, and beta testing is a big news, PS4 exposure also led to the success of the steam platform.
At the same time, Corey said Psyonix is very fortunate, when the analysis of a game success, need to see success is not replicable, with the timing and many other factors, but as a developer, you can try to make the probability of success, such as careful selection of online time and so on.