I see. Well I don't have anything really organize to really explain it in the best Detail, I'll just give out some quick reasons and such
-MK11 Came to the Switch back in April of 2019. I know this doesn't automatically mean Mortal Kombat in Smash. what it does mean is that WB Games/Netherrealm have came back to Nintendo after years (and MK9 and MKX) Missing Nintendo Consoles. Plus around the time of the release of the game is when FP2 was probably being thought of and such
-Ed Boon has been very supporting of wanting Mortal Kombat in Smash. there's been interviews where he expressed interest in Smash, and also Tweets. nothing special there though
-In Interviews with Ed Boon, Ed Boon hasn't had a Response that would look bad for the chances of Mortal Kombat characters. I'll maybe post the video link and such, but the wording doesn't Confirm, nor explicity deconfirm either, and he doesn't go into how He and Nintendo talked about the potential inclusion. If you look at the Doom Interview, the guy went into detail into the talks of Doomguy into Smash and how Nintendo didn't take it too seriously. Ed Boon interview wasn't like that
-Kind of like there was that poll with Dante with what Kamiya character would you want to see in Smash, there was a Mortal Kombat Poll of whether you want to see Scorpion or Sub-Zero in Smash. Scorpion won. This was back in April of 2018 I Believe
-Mortal Kombat has been pulling numbers and doing really well the Past Decade, starting with MK9. I Mean honestly i don't think there was a period were they weren't doing well, but This Era of Mortal Kombat is Doing REALLY Well
-In terms of what audience Mortal Kombat appeals too. It's a different audience than from the other characters in the Pass. Mortal Kombat recently houses large Playerbase on PS4 and also Xbox, but it also could appeal to Nintendo at the same time because Mortal Kombat has had a long History with Ninten, along with MK11 being on Switch already. It also appeals to a More Mature Audience, Kind of Like with Joker, though MK is Bigger game and due to the difference in Genre, differs in Audience. The Audience is also different from Terry as well, Due to the more mature nature and just the fact Mortal Kombat has way more causal audience than King of Fighters, or even other FG Suggestions (Like Guilty Gear)
-On the Japan point, I will have to do more research into how Well Mortal Kombat did before CERO came in (I Don't believe it was the most successful). even then though, I do think Mortal Kombat's inclusion would actually add some intrigue to the Pass. I've heard that some in Japan think Mortal Kombat is some Urban Legend, so Smash, which is a big Game in Japan, having this "Banned" Franchise as DLC might provide some intrigue. I Know Injutice 1 was released in Japan and didn't do so well (and DLC Had Scorpion), but The barrier of entry is much wider considering Smash already has alot of customers from the base game. Injustice didn't have that. Of course they might not just care, but it's something to consider
-Ed Boon has expressed interest in Street Fighter Vs Mortal Kombat. an actual game has been stated not to work, however with Street Fighter already in Smash, this idea could be replicated in Smash. It's kind of that Same point with Dante vs Bayonetta.
And then the following points are more Conspiracy based, but they could lead to something
-Arc Systems have a Spirit in the game currently with River City. I don't think they would Spoil Arc's System Inclusion if we were to get a character, but perhaps we could still see more content in More Spirit events or Mii costumes, more precisely of guilty Gear or Blazblue, both fighting games. there have been trends of Fighting game costumes coming with other Fighting game characters. a Point towards Scorpion
-M Theory. Scorpion is not the only character affected, as Other Candiates like Dante, Ryu, Master Chief, Travis could also be affected by this, but it also Helps Scorpion though
-A Theory is that Min-Min was revealed this early because she's gonna appear in a Fighting based trailer. She has that Asian Inspired design. Scorpion is also Asian Inspired as well. This is Very tinfoil hat though
-a Gamefaqs user by the name of Calebtine came onto Smashfaqs and said Scorpion was Fighter 5 and would be revealed in November. However in a later post he retracted the Statement as a misunderstanding from a friend. There's more detail in the following Links
https://gamefaqs.gamespot.com/boards/234547-super-smash-bros-ultimate/78120584
https://gamefaqs.gamespot.com/boards/234547-super-smash-bros-ultimate/78348744
However, while it could be fake, One thing I'll say is that Netherrealm has a Nasty history of being leaked. they got their full Base roster for MK11 leaked Through Picture, and I believe real leaks have been posted straight to Gamefaqs before. This post could be indicative of that.
-Sakurai might love Ninjas. Bias Theory baby
I need to go ahead and do a more in depth documentation, but I believe Scorpion might have signs pointing towards him. He fits the Timeline of when FP2 would have been chosen, and he has Perks that other characters (even other Western Characters like Crash) doesn't have. It doesn't sound impressive probably, but I'm gonna stick by my convictions on this one.