Apparently people found assets in the multiplayer build that has the year 2069 on them, which is 3 years after the events of Black Ops 3. Meanwhile, the devs said this game takes place between BO2 (2025) and BO3. So I guess the leak about campaign getting scrapped mid development was right. The shitstorm that hit Infinite Warfare scared off Activision so they told SHG to dump Advanced Warfare 2 and make WW2 (which was a rushed piece of shit) instead. Same thing probably happened to BO4, campaign got too futuristic (IIRC it would have involved time travelling and shit) and they just couldn't tweak for fix it enough for the approriate aesthetic, or narrative, or gameplay, or set piece or anything related, so they simply removed it.
There's also this one from the cinematic trailer. Corvus was the AI generated by DNI that played the antagonist role in BO3 which is impossible to exist before that game's timeline.
Those things aren't directly related as it's not high profile releases like a Call of Duty game that are hurt by Valve's lack of quality control.
EA did this years ago so the real question is what took Activision so long.
To be fair they have a less prolific catalogue than EA in recent years, they live off COD, Destiny, Skylanders, Candy Crush and MLG esport, not enough PC products to justify completely moving off Steam.
They gave a shit about Destiny 2 on PC and it became their biggest PC launch ever, they didn't have beef with Steam and Valve like EA but this showed that they can capture a huge audience on PC, and (bear with me for a sec since this probably sound retarded) I think with the inclusion of Battle Royale - the most popular genre on PC at the moment - Activision wants this game to have a healthy lifespan even with the yearly release schedule so they can milk it as much as possible through microtransaction.
I don't think they want their entire catalogue to be exclusive on Bnet - Crash Bandicoot, and probably Spyro remake, are on Steam for example. But their main money makers will. Call of Duty is my guilty pleasure and if this decision leads to a good PC port, then so be it.