Hi there, hakim265.
To clarify, you used both Safari and Chrome to view a YouTube video and still observed the same issue with 60 FPS, correct? If yes, have you noticed this issue with other videos (besides YouTube videos) or only when watching YouTube videos? We want to make sure we fully understand the issue you're encountering.
If you haven't already, you could see if restarting your iPad might help: Restart your iPad - Apple Support Restarting can refresh iPadOS and possibly help unexpected issues.
You'll also want to ensure that your iPad is fully up-to-date, as iPadOS updates can sometimes also help resolve unexpected issues: Update your iPhone, iPad, or iPod touch - Apple Support
Take care.