A Monthly was headlined by a newer Call of Duty game just a few months ago. I’d guess that they expected COD:WW2 wouldn’t be enough of a reveal on its own.
Since WW2 is present presumably entirely in an attempt to drum up further interest in Modern Warfare 2019, WW2 needed to be revealed (and playable) from the start. That means the month needed to launch with multiple reveals. I’m a little surprised both Crash and Spyro were revealed. I can only assume that is because of the interest overlap. Even if you don’t want COD, Crash + Spyro together might sell you on the monthly, where one alone might not. I admit, I’m moderately tempted myself due to Crash and Spyro, while one alone would have been too much of a gamble to even consider re-subscribing.
At least a couple of game news sites seem to share my sentiments. Headlines at both Destructoid and PCGamesN didn’t even bother to mention COD.
Destructoid: "The Crash Bandicoot and Spyro trilogies are $12 at Humble Monthly"
PCGamesN: “Get the Crash Bandicoot and Spyro remakes for $12 in the latest Humble Monthly bundle”