Now I know some of those people tend to have embellished things in the past so can only relay how I was told it went
MLB said move to Xbox, Sony replied no, MLB said move to Xbox or we take the publishing rights elsewhere
Heh, cool. Well, regardless of how things may have gone down at the time, I doubt SIE are broken up about the game being on other platforms. I think they'd currently be more concerned about publishing rights. My running theory has been that the publishing rights would revert back to SIE after a set number of years, so it could be that has been a factor in when SIE would announce a mobile/PC MLB game if they wanted to wait until they could have full publishing rights across the board. That way they don't have to give MLB the publishers cut off of all the sales/mtx
This game has been announced almost exactly 6 years after the renegotiation was announced (off by 6 days) so perhaps the rights have now reverted. I guess we'll see if SIE winds up publishing MLB26 next year on Xbox and Switch, and if a PC port gets announced.
MLB is the owner of the MLB rights, its rights don't 'revert to Sony'.
Sony pays MLB to get the license during some years, they agree. Once the license is going to expire, they negotiate a renewal of the license to let Sony use it some years more. And keep doing it multiple times.
At some point in one of these renewals, MLB decided that if Sony wants to continue using the IP they must port it to other consoles. Sony acceded to port it but not to publish it, so MLB created a game publisher to publish the Xbox and Switch versions.
This time seems they agreed to make separate game for smartphones, also made (like the game and its ports) by Sony San Diego. It isn't clear who will publish it, but I assume Sony because unlike when they made the previous negotiation they're now open to publish on PC, rival consoles and mobile.
From Sony's point of view now that they want to push their mobile games part side, when looking at the available IPs to bring to mobile, MLB The Show is one of the series that has a best fit. So maybe Sony is the one who asked them to bring it to mobile. And pretty likely if this year MLB The Show expands to mobile, it may also expand to PC too the next one, and published by Sony (even if sport games don't sell in PC as well as in console).
A similar case of Death Stranding: in the first one Kojima wanted to port it elsewhere, Sony didn't but acceded to port it and let him find another publisher for the other platforms. Nowadays Sony is open to publish outside PS, and Sony will be the publisher of Death Stranding 2 on PC.
SIE's current live service initiative and mobile initiative were formulated around 2019/2020
No, the PC+GaaS+mobile push started before Jim Ryan and Hermen got in charge in 2019: The PC ports of Horizon were also stated by Shuhei Yoshida and Shawn Layden who also greenlighted Helldivers 2 in 2016 or games like Condord, Horizon Online or pretty likely Gran Turismo 7 in 2018.
At some point they had Japan Studio making mobile games, something Hermen did stop around their restructuring, greenlighting them Astro Bot for the internal development team and tasking their external development team to publish games not only developed in Japan, but also in other Asian countries (and greenlighted them Stellar Blade, Death Stranding 2, Marvel Tokon, Lost Soul Aside or Physint).
Nowadays mobile games take almost as much time to be done as console games, make sure games like Destiny Rising, Horizon Steel Frontiers or this MLB The Show take the same time than equivalent console games. As an example, Bungie and Netease signed their deal for Destiny Rising back in 2018 and the game released now.
I can't read the fine print on my phone, is SSM actually developing this or is there a co-developer?
(I'm sure there are already lots of codevs working on MLB proper, it's not like this would take time away from the main game... Or that the main game has really shown much serious investment of time in redevelopment over the past few releases. I'd just be surprised if a mobile game was maintained in house by Sony.)
Developed by Sony San Diego (they're the ones who make the console game, not Sony Santa Monica), published by PlayStation Mobile Inc. Pretty likely like any game (including the big mobile games) it will have several support/outsourcing studios helping to codevelop it.