WildCard,
You're right, he wasn't going that fast. I'm glad you brought that up because it shows that sometimes speed is not the issue. I watched the video a couple of times, and while I didn't study it in depth (the internet speed on base is is so friggin' s-l-o-w), here's what I saw.
He may have been entering the turn hotter than he felt he should have been. I use the word felt, because it's all relative to what the rider perceives. Two important factors come into play here. He positioned his bike to travel along the inside of the curve along side the yellow line, you can see that. He also rolled off the throttle, you can hear that. When he rolled off the throttle, he loaded up the suspension, meaning the bike squatted down. This happened as the forks and shocks compressed because they were no longer being elongated by steady or increased throttle. Riding on the inside of the turn along the yellow line, he had nowhere to travel but outside. With the suspension loaded up, the inside started to drop and he started to drift outside. He tried to compensate for that by leaning in. All that did was lower the bike more and the the primary started dragging. As he continued to drift outside the bike levered up on the primary and slid out.
A few things may have made a difference. It might have been better for him to brake and get his speed set before entering the turn. He would have done better to have taken an outside - inside -outside path of travel with a later apex. This would have given him more room on the exit. He also may have benefited from steady or increased throttle right after braking and continuing all the way through the turn. Not hammering the throttle, but steady or increased. This would have unloaded the suspension, stretched the shocks making the bike taller, and thus being able to lean over more due to increased ground clearance.
Those StreetGlides are pretty low. I had StreetGlide shocks on my Ultra and used to drag it all the time in turns. I finally switched back to stock height shocks.
But I could be wrong about all that.