After OG won TI8, Ana their main carry (homegrown Aussie boy), took a break from DOTA in general. During that time Team OG didn’t win many games. When Ana returned, they started winning again and eventually qualified via the DPC to get into TI9. OG have stayed in the upper bracket and even defeated their rivals from last years grand final PSG.LGD. This set them up with a slot in the Grand Final. OG get a lot of their success by keeping a relaxed attitude to winning (did you see that Ana body block??) and they have their own game style, which others try to replicate.
It was a huge effort and a well-deserved win for OG, congratulations!