[AgentME]

This is an issue with extensions that run code on webpage DOM. It's very popular for extensions to modify webpages. Chrome supports extensions like this too. I might even guess that more than half of extensions do this.

>Why would anyone run Angular on a browser page? It would probably conflict with existing application.

Adding additional widgets or tools directly within an existing webpage is a common thing for extensions to do. And if you're adding a lot of UI, you might want to use an existing UI library like you would on a normal webpage instead of doing all the DOM by hand. Not all UI libraries work out well for this apparently.