Same. I think I still read 5-6 of Diana's articles spread out before I stopped. When the account reached 5K followers, I even congratulated them lol Soon after, I had written this article and blocked them.
I never got more than a single interaction from David. I think... I could be mistaking him for another, it was a while back.
Either way, between his About Me cover photo, his LinkedIn endorsements, and his being part of the Author's Guild (which seems to have a lot of legalities involved), I believe he's real. He seems to be a full fledged author of books. That said, I'm starting to think I should do a deep search on him, read at least one of his books and everything, if I'm going to say I know for sure. It just strikes me as overwheling if he's not real.
DM has no background, and even the account's original profile photo was from pixabay.