Rumney, - Learning to play by ear was my guess from your question.
Without putting down the lady on the video, I have played and known hundreds of real musicians who played professionally by ear and while all understood the circle of 5ths, to my knowledge none used it or thought about it either actively while playing or while learning to play, by ear.
If you want to learn to play by ear, it will be much more useful to understand common chord progressions by the number system, which is key independent. The number system is simple, just each chord based on the note of the scale - so in C, chord 1 is Cmaj, chord 2 is D minor, etc. Look up chord numbering systems on the net, but don't at this time get too deeply into the more sophisticated versions like the Nashville numbering system where many accents and variants can be added for more advanced players.
So the simplest chord progression using the number system is 1;4; 5;1. Chord 2 and 4 are similar, so another variant is 1;2;5;1. Another very common variant is 1;6;2;5;1. ie in key of C it would be C, Amin, Dmin, G7, C.
Those three chord progressions above cover 80 % of the popular songs written for at least 80% - and often 100% -of the whole song. Start by nailing these, and then add songs which have small excursions from these like chord 3, or making chord 2 or chord 3 major instead of minor. You will soon get to hear them coming by ear.
Don't worry about the relationships on a circle of 5ths. The secret to playing by ear is to start with a small amount of knowledge like the 3 chord progressions I have given above, then build on it by experimenting, a bit at a time. As you advance, you might find the circle of 5ths useful to understand for more complex songs, but frankly, by the time you find it useful, you are unlikely to really need visual aid, because the relationships will just make it will just make obvious.
Later, learn and introduce diminished chords by realizing another common device is to slip in a diminished to lead through or add color to one of the above progressions. Try to find the right chords by are, then look at fake books to see how what you thought compares with the right chords, and how real songs progress,. And instead of seeing the chords as individual things in a song, learn to see them as sequences of numbers, and you will then start to understand how most music is 90% repeating patterns. Combining this with listening to yourself and anticipating the sound of a chord in a sequence is what playing by ear is all about.
Mike