Why are all my Characters Health bars linked?

I’m looking around, I saw:

https://forums.unrealengine.com/development-discussion/blueprint-visual-scripting/1593321-multiplayer-health-bar

Also this ( don’t copy the code ):

https://forums.unrealengine.com/development-discussion/blueprint-visual-scripting/103763-multiplayer-widget-explanation-why-this-is-working-and-that-not