If you want to start getting your focus back under control, give meditation a try. It's a gentle tool to will help you get you understand how your attention works, and, with training, will give you back the control you need.
Serious suggestion: stand while you watch the video (Youtube on a TV helps here), use a pomodoro timer to do it in bits.
I also find I can watch a good bit of a complicated/technical video while walking on a treadmill/stairmaster at the gym. Just enough noise of other people, and the determination to do 45-60 minutes on a fitness machine replaces the determination required to get through a video. Doing it 3 days in a row feeds the motivation cycle in me. After day 1 I'm itching to get back to the gym and get back to the video to do another "episode".
you don't have to do it in one go, i usually do pen and paper, 45m-1h of video time (~2h wall time)
and often redo the same exercise a couple of months later
If you want to start getting your focus back under control, give meditation a try. It's a gentle tool to will help you get you understand how your attention works, and, with training, will give you back the control you need.