Marcus Mariota's Struggle in the NFL

Mariota wasn't bad last year, especially when he was running. The thing I don't understand is why not keep the who's the backup in Atlanta Taylor Heinecky now? Why not keep the guy who knows the offense? Because he's not going to be playing. Mariota apparently, so he's in this quarterback thing, right? That's Netflix show. So how's he coming off there? I've watched four episodes and it comes off like he comes off fine.