Yeah that is just it, after reksai took the cass ult the gank was over. Faker didn't even bother flash early - he was that confident.
It's a hard place to be in as C9 there and honestly, 99.9% of the playerbase would have flashed the moment they came out of the bind/knock up but clearly here that wasn't necessary.
Scary how confident he is and not unjustly so, that play alone would tilt most people because it was perfectly executed and he played them flawlessly.
Faker is too good. Against almost any other pro they get that gank off, but against faker they need more guaranteed ccs because he's just so confident at estimating damage.