One likely reason they're still on X is so those that didn't get the memo to use their app or otherwise can't still can still get alerts. Switching to multiple accounts would require people who likely wouldn't notice to follow the others, and those that would do that would hopefully have downloaded the app. And yes, if a person isn't noticing they need to get the app they likely won't notice a critical alert, but when you're dealing with people's lives everything counts.

Right, because it's not on the platform to remain how it was. It's now the users' responsibility to completely change how they interact with the service so they can have the same functionality.

At that point, I think it would be more reasonable to move people to a more resilient network, like someone else recommended, Mastodon would be good for this.

And that's not to blindly shill for Mastodon. It genuinely happens to do this one thing particularly well.