Shows hammerhead handle removal, set new handle, and finish the head.
Mr. Hardware likes to hit the bottom of the new hammer handle down with the hammerhead down, he finds he aims better.
He understands others swing up, with the hammerhead up, the weight resists the head from moving, and the hammer blow drove the softer wood to seat the handle.
Just don’t wack at the hammer head, side-to-side, to drive it down on the new handle. It won’t be “tight and straight” for you.