I think different animals, considering Nintendo properties like Pokemon and Zelda as vastly different than Mario and his pals. They interact in some games sure, but its not like you're building 2 specific lands based off the same films, they're building different IPs essentially. They're different "Universes" shall we say. For example, the HP films all take place in the existing theme park lands. Thus, having them in the same park Imo would be a bit odd. Splitting them up to 2 parks makes sense not only business wise, but thematically as well. London isn't right next to Hogsmeade, so they had to build it in another park.
Pokemon and SNW are completely different Universes. Having those in the same park is not crazy to think about. Also, you now have 3 parks to play with, and not 2. Makes the decision a bit more complicated than "Lets just put this in the other park to spread attendance", you have 3 of those now. I don't disagree its a bad idea to put them in IOA, USF, and EU but I don't think its as simple as that.
Thank you for making my argument for me.
Super Mario = Huge IP that anchors a new park
Pokemon = Huge IP (that already has Kidzone-specific plans)
Zelda = Big IP
Business says, after you open a new product, you invest in the old. That's the only way to ensure the old doesn't lose relevance.
2023 - Open EU (with Mario and DK, which Hollywood doesn't have)
2025 - Open Pokemon in Studios
2026 - Luigi's Mansion in EU
2027 - Open Hyrule in Islands
2028 - Replace Mummy
2029 - IoA Attraction and MiB/Simpsons replacement
2030 - EU addition (Kung Fu Panda or Far Far Away)
Smaller updates, events, etc fill the gaps.
Now, people who go in 2023/2024 have to go back in 2025/2026 and visit TWO parks. Then go back again in 2027 for Hyrule and visit THREE parks.
Putting all of Nintendo in one park is, frankly, a terrible idea. Especially because there is no real connective tissue between the various IPs.