Rockstar spent some time changing things around Steam listings which apparently made all the Rockstar Steam listings disappear for a while and came back later with some amazing add-ons to them. Midnight Club 2 was listed down there for a few minutes, also users discovered that Max Payne 3 and LA Noire's Steam versions now included free DLC's with them.
Midnight 2 was released back in 2003 and was delisted on Steam in 2018 which was upsetting. It was more than just a street racing game; it was a time capsule for gamers of the 2000s.
Since the Steam incident, Max Payne 3 and LA Noire's DLC are available in the store at no extra cost and are already included for free even when you buy the basic versions of both games, except for the VR Mission on LA Noire. Max Payne 3 was there released for PC in June 2012, while LA Noire was launched in November 2011 them getting these free DLC's now doesn't make much sense. Few calls this a stealth marketing move while others see it as a technical glitch from Rockstar but since we receive free stuff, so these changes are happily welcomed as it's a win-win for the end users.
While other than this, the major change here is that these games were updated and the support for 32-bit operating systems have been 'deprecated' which means to disapprove or replace with new source in technical terms.
Overall this was an amazing surprise from Rockstar to call it a marketing gimmick or a glitch, the users who managed to get their hands on Midnight Club 2 and the free dlc's which are still available are indeed happy with this.