The white string is the closing loop - the pin goes through that to hold the container closed. To open the canopy you throw the pilot chute which pulls the pin free of the closing loop and allows the main canopy to come out of the container and open. The closing loop passes through those two metal grommets and is then secured by the pin.

It looks like the loop was wrapped around that piece of material that he's holding between finger and thumb. If the loop is entrapped then potentially the container won't open fully, or will cause some other form of entanglement meaning the canopy will only partially open.

Looks like he saw this and deployed his reserve but the entanglement meant his main didn't cut away fully. Then his main and reserve entangled and he had what is called a ball of snot overhead.

He was lucky that through skill and/or good fortune he was able to separate the main and reserve canopies and end up with a two-out, in itself a very serious malfunction but at least something with appropriate emergency measures that can be performed. So he was left with a reserve with twisted lines and a balled up main.

The reserve was not fully deployed so he fiddled around to get the slider all the way down to the line twists. Landing with line twists, with a two-out and landing on the runway is obviously not a desirable situation but looks like he wasn't seriously hurt.

Very lucky boy as he had a series of malfunctions that progressively resolved to result in a survivable emergency landing. I'm assuming that through a packing error he somehow wrapped the closing loop around that tab of material. So he was doomed to this outcome (or worse) before he even got on the plane.