I dunno, why are a group of people searching for a magic lake in an area where a magic lake exists due to the point of divergence.
The thing is that Disney's Marvel(tm) effect isn't just one single issue. You see people constantly running into it and trying to blame one thing or another, like how with Book of Boba Fett everyone was focusing on the new circular CGI set Disney uses and how it 'forced' the show to suck.
It didn't.
Certainly, it had an effect on the show, yes. But one thing alone doesn't cause the whole issue.
Yes, there can be a valid an logical explanation for Spanish Conquistadors far North. I even fully agree that it makes sense and would happen if there were rumors of something magical or profitable.
But that's not the issue. The issue is that, along with a thousand other things, it's done frivolous, pointlessly, and aimlessly.
It just amounts to 'Oh, the Spanish are here for some reason. That just happened.' Followed by the next weird random thing Disney throws at you that's also a 'That just happened' moment. Which one after the other come off as cringe as when the dialogie is literally, "That just happened.".
Compare it to Code Geauss for example where the Super-British are invading Japan. Why are the British invading Japan? Because it's an alternate timeline where the British never lost the USA and became even more powerful. Does this have any impact on the rest of the story? Yes actually, the British Superpower is actually explored and is a central part of the setting, plot, characters, and style.
It's not just a random thing that happens like Disney constantly pulls.
And it certainly doesn't have an obvious and in your face political motive like Disney does either. You can FEEL the politics of having Conquistadors in Northern America because Disney's aggressive genericness is overwhelming. Even if you quickly consider and justify Conquistadors going anywhere to plunder as making perfect sense, you still
know that it's just Disney not wanting to make people mad by having British/American settlers be the unambiguous bad guys. There's no getting around it.
So in this manner everything Disney makes just ends up with an unsettling sense of unease and discomfort because all of this just accumulates and drags everything down.