Not every brain works the same way, and everyone'e learning preferences are unique. My preference, because it underpins true understanding over rote memorisation, includes seeing connections and derivations from first principles. So that video, whilst effective, leaves a gap.
Here is how I was taught to deduce, not remember, the order of accidentals:
The major scale is constructed from 2 identical 'Tetrachords', each consisting of a tone/tone/semitone (W W H) and separated by a tone (W)
(Etc....)