The code on your page is not generated by ARVE. You are using this plugin or something there are “fusion-video” classes and stuff but nothing ARVE generates.
You should disable other 3rd party things doing stuff with video. You should also use the new shortcode:
[arve url="https://youtu.be/Gx9XeC_J3A4″ mode=”lazyload-lightbox” maxwidth=”150″ align=”left”]
If you have a lot of old shortcodes the old shortcodes do still work with ARVE. I tested your code and it works fine. You can also change the youtube shortcode to something else in the ARVE settings page to avoid conflicts with other plugins but then you would have to rename your shortcodes anyway so best change them to the new shortcode. There are plugins for replacing content on posts. You could replace
[youtube id=" with
[arve url="https://youtu.be/ if all your shortcodes start with id.
But better you get rid of this fusion video thing if you can.