As someone who never had these dreams... Why is it scary?

I'm trying to understand what these dreams are and why so many people had them (also apparently only as kids??? have any of you all ever dreamed about this as teenagers or adults?)

But i'm struggling to understand what was so bad about it

I saw descriptions and drawings and animations, some that others were saying that it perfectly portrayed how these dreams were and that it even triggered them

But all i see is just shapes that go big and small, and i just don't understand what's scary about that

What was scary about these dreams? How did they felt and, above all, WHY did they felt like they felt?

"i got so scared" with what exactly? the ball?

I'm really trying to figure out more about this rabbit hole