His slow and mobility was huge in a lot of those chases. To even keep up in a game like that while being so far behind on gold is huge. The bigger issue is that they didn't just farm it up near the end and felt the need to keep being aggressive even when the enemy team was baroned up. They got caught out and initiated on instead of being the initiators just once and that was it, game over.I feel like the Rengar pick was Dig's downfall. He wasn't doing any damage so he was only useful for a stun and the surprise factor, and if you wanted a stun bot they could have taken a number of other champs that do it better and more reliably.
Compare Rengar to Lee Sin that game. He even crushed him once in a 2v1.