Every element’s id needs to be unique. You cannot use the same id for more than one element.
There Can Be Only One, Highlander.
Imagine you are communicating with your team on walkie-talkies using codenames. Now imagine 5 people are using the same codename “Eagle1”. You want to talk to “Eagle1” at the base, but the 4 other people in other parts of the mission all respond when you ask for “Eagle1”. Chaos.