Any idea why this user did not rank up to Newbie or why his posts can not be seen on the forum?
Maybe all of the posts were moved to trashcan. This means technically the posts are not deleted but as regular users we can not see them. Since they are in trashcan, perhaps that's the reason the activity did not count to.
You are correct. All of AIbotBTC user's posts were in one single topic, the topic was moved to Trashcan. And since Trashcan is not available to ordinary users, then, accordingly, all his posts are not visible to the ordinary user, but they are displayed in the user's profile, as they have not been completely removed from the forum.