Why don't Angular scripts work from a migrated site to Joomla CMS?

Question

JavaScript

Why don't Angular scripts work from a migrated site to Joomla CMS?

If you put aside the questions why, then here's the point: you need to transfer the site, which is in the .htm, .js and similar formats, to a new site on which Joomla. During the transfer, styles, pictures, fonts and layout got up, but JavaScript refused to work.

I understand that it is strange that it should work at all, but outside the theme and CMS everything worked, in a simple layout everything worked