@PirateRoberts That is bloody impressive! I think a lot of it, (once you have the strategy) is having the confidence to implement it.
It is and it isn't - putting to one side the part at 73secs - when you are only hypothesising about a strategy and are then maybe 60secs away from trying an idea again - if you fail - then that is a lot about confidence, but the stuff in the video is all pretty easy once the timing is explained and it is broken down into basic moves. There's not a lot you can get wrong if you use the d-pad at first.
As said previously, the part at 73secs is probably an exception to that, and even now I'd struggle to do that part 10/10 times (after a practice). What you can do to build confidence is to count when you've did 3 jumps (so you are on the first block of the 4th - different coloured – step).
At this point, just jump back to the far left side of the previous step(the 3rd step); run half way across the step and jump up to 4th step again. If you then jump back down again and run again, you will eventually get your timing so that you can run the full width of the 3rd step and gain enough speed (and be at the correct timing) to leap on the second block of the 4th step in one jump.
You would then be faced with the same problem again, when you jump on to the lower block of step 5, but now you are between two steps that are made of two blocks. So you'd just jump back and forth between the top block of step four and the lower block of step five, until the timing was right to run the full width of the top block of the fourth step 4. The confidence comes from staying alive for a longer period on a difficult section, even if you don't feel like you actually got any further when you fail.
In that part of the video, the most important aspect of the strategy is seeing where the feet of mario lands on each block; typical you want to land nearer the beginning of a block to have more space to run to pickup speed before you jump to the next block.