The epiphany for me was realizing that there are two separate sources of thread. The bobbins are out of sight so I was puzzled for a long while as to how the magic works.
Aahhh, didn’t watch the video, but that makes sense. I’ve always felt like sewing machines were some sort of dark evil magic that couldn’t possibly work.
Yes, elementary topology clearly shows that sewing machines don’t exist in three dimensions.
For me the realization that the top thread's loop goes AROUND the bottom thread's entire spool is what made it click for me originally.