Was this a mistake by Marvel Comics?
When Frank Castle gave up the mantle, fans were upset. To some, Frank Castle isn’t the same if he isn’t the ruthless Punisher. Now, someone new is taking his place. Punisher writer David Pepose (Savage Avengers) said, “For existing fans of the Punisher and for new fans, this is a story that’s not going to sacrifice any of the attitude, any of the action, and we are not letting the pedal off the metal.” He also added:
"“The man might be different, but the punishment remains the same. I wanted to introduce the Danny Ketch to Frank’s Johnny Blaze.”"
A brief look into comments on comic book social media will show people upset about legacy characters. You’ll see comments like “Laura Kinney isn’t Wolverine” or “Miles Morales isn’t Spider-Man” when, in fact, they are. Not only has Marvel signed off on the new characters taking over classic mantles, the writers did as well. They make it a point to have their mentors give them their blessings within comic book stories.
It will be a little different with Frank Castle. He won’t be around to give Joe Garrison his approval. Plus, as long as Garrison isn’t hurting innocent people or putting them in harm’s way, it’s doubtful that he’ll care. However, don’t be shocked if Frank tries to help him not make the same mistakes he did.