I was given some white oak lumber about 35 years ago when I was building a small barn. I couldn’t drive a regular pointed nail through it to save my arse.
A “well seasoned” older man told me to grind that point off to a blunt tip. Everything was right with the world after that. Seems counterintuitive, but I could drive the nail without bending it.
I think the pointed nail caused so much friction around the perimeter of the nail, and the blunt tip just busted through. I’ve never used a fence post driver, but I can imagine similar circumstances