"What is going on here?
And. . .more important. . .why?"
I dunno and I dunno. I apologize for going all berzerker. I won't even try to justify it by tryin to explain what set me off.
Measure twice, cut once.
Look at the nail, not the hammer. Watch the fence, not the blade.
If you hook your thumb over your belt you won't hit it with the hammer or leave it layin on the saw table.