I saw on some youtube video that he is using a 4 nvidia GTX 1080p graphics card to mine bitcoin. I'm confused how these graphics card will be able to mine bitcoins.
You may try to mine Bitcoin with you GPU, but even if a pool will accept your shares, you'll get only a few cents per month, while paying a lot for electricity.
Nowadays nobody mines Bitcoin with GPU.
One idea would be that the recording is old. Years ago Bitcoin was indeed mined with GPU (even CPU in the beginnings).
Another idea is that he was actually mining either Bitcoin Gold, either other altcoins. There are mining pools that automatically convert your earnings from altcoins to Bitcoin, which may make somebody think he's mining Bitcoin, especially if the setup is Nicehash-like, meaning mostly automatic.