This would be a huge gamble, because you could end up with two mediocre games or even only one mediocre game and a dead one. In the short term, yeah, it would make sense for them, because AOE4 would sell a bit more. But in the long term, the Age of Empires franchise as a whole would be hurt, because of the declining interest in its "ace", which has always been AOE2 since it came out. Sure, AOE2 wouldn't die, but it'd be back to like 2017 in terms of viewership and sponsor interest, which would be a huge farewell to events like Red Bull Wololo and maybe even Hidden Cup and King of the Desert. You may not really care about AOE2 (which is legit, don't get me wrong. I personally have zero interest in AOE4), but let's agree that "the health of the overall AoE franchise" can't depend on pushing the latest one while ignoring the most successful one for some time, hoping that they'll become equally successful in the long term.
I don't really think anyone can forecast what will be best for the overall franchise at this point, so I wouldn't agree that focusing more on AoE4 is the wrong choice. What do you think Microsoft's main key performance indicator is here? My guess would be Game Pass numbers, and AoE4 has shown more potential for Game Pass sales than AoE2. Maintaining interest for Game Pass players is considerably more profitable than steam sales, so I would hardly consider AoE2 to be the "ace" at this point. Server and development costs for AoE2 are probably only offset by DLCs.
AoE2 has survived 20 years and maintained a stable player base, so I would say it's a pretty low-risk gamble to redirect some resources toward your new RTS game than it is fund extra tournaments for AoE2, which doesn't seem to impact player numbers on steam at all. AoE2 tournaments like HC and KOTD are part of the livelihoods of T90 and Memb, so I doubt they will be going away in the future regardless of what MS chooses to do.
Wow, I'm amazed of how people on this forum think that swinging some hypothetical money will somehow give them the higher moral ground. If you want to spend you money supporting AOE4, you're literally free to. There's a lot of AOE2 community members who have spent their money for years supporting channels, tournaments and even showmatches, but I hardly see any of them here saying anything about it. If this community doesn't interest you, it's fine, you're free to support another one.
I think I contributed about $50k to AoE2 casters, players, and showmatches in 2021, so it's not really hypothetical. I'm not looking for a moral high ground. I'm saying the reaction of (some of) the AoE2 community to another game in the franchise has been off-putting, so it's unlikely I would want to contribute more to it in the future. If you're concerned about future sponsorships for AoE2, maybe you should reflect on how toxic community reactions can also negatively impact the health of future events.