3b1b is definitely in my top 3 favorite youtube channels. It may be my #1.
Spoiler alert:
The spirals arise because he's wrapping whole/integer numbers around a circle with an irrational circumference (2*PI), so that's kind of trivial and has nothing to do with their primality (which he concedes in the video). But the gaps and other stuff are still pretty interesting.
And I might not even pick that hard, except he named the video after the prime spirals, when they're really just integer spirals, like some kind of click bait.