Complex sentence: This number rose to 500,000 by January 2016, and to his first million by February as one of the fastest growing youtubers amongst controversy between him and "reactors" on youtube.
Split into simpler sentences: This number rose to 500,000 by January 2016, and to his first million by February as one of the fastest growing youtubers. This growth came about amongst controversy between him and "reactors" on youtube.