Shouldn’t the creators of the original content have a say though? If someone made their youtube video private that probably means they don’t want people watching it anymore.

If that was a consideration, wouldn't they have hosted it themselves?

Even super small businesses that rely on training videos as paid income don't host things on YouTube because they want more control over the content.

it's likely the video creator used youtube so they could create an audience much more easily. Or didn't have the technical know-how to host a video themselves. Or they didn't expect making their youtube video private in the future would be an issue, or any number of reasons.

It's much harder to imagine someone wanting to upload videos to youtube, and then considering the possibility that something might change in the future that makes them want to make their videos private, and then deciding they are going to host the video on their own instead. Unless it's a tech person or someone making extremely shady videos, this scenario is much more unlikely than the opposite