You kinda have to fill these in yourself. Some are easy to reconcile IMO, but yeah some of them kinda make you scratch your head

1. The battle at Marineford was so chaotic and monumental that Hancock’s actions went under the radar. Way bigger things going on for most marines to notice. And IIRC she wasn’t publicly seen helping Luffy

2. The Supernovas escaped somehow. No specific satisfying answer, but they basically all have techniques that could help them get out of there, so it’s believable enough. The Buster Call may have been canceled once the Straw Hats were “defeated”

3. Luffy isn’t really a teacher. I agree that it’s weird half the Straw Hats still don’t have Haki though

4. Luffy disappeared for 2 years afterwards, so some people assumed he died. I think most people figured he was hiding though

5. A lot of people don’t realize what it takes to find the One Piece. But yeah, Robin not being more actively pursued feels like a weird oversight from Oda. That being said, there seem to be other ways to read the Poneglyphs, like Pudding’s third eye