Agree with above.

Though, IIRC, in the past I occasionally interacted with such accounts, and that I noticed there are accounts from time to time who got up and necrobumping threads, or pseudo-necro bumping, most of the time, it's best to do nothing and ignore them.

More often than not, those posts are pointless that add no benefit to the necromanced thread, given the topic has long been resolved or no longer become relevant. Or perhaps those post are borderline "OOT" by promoting their service without seemingly bother to grasp the nature of the topic in the thread, with the sole purpose of promoting their platform, like [urlhttps://bitcointalk.org/index.php?action=profile;u=2748297;sa=showPosts]this one[/url].

Best approach, most of the times, unless the post contain misleading information, is to ignore them, as engaging in those necro-bumped post will make us also bumping that thread [who deserve to be silently drowned by other threads in peace].

As for why... hmm... sold accounts? Or perhaps like SheldonCobb above, having a bitter experience with one or two projects and decided to spare no mercy on the entire crypto platform.