Bad thumbnail image quality

Hi

I used this PNG image: https://share.getcloudapp.com/5zuGb9jm for this video: https://www.youtube.com/watch?v=21rmUNaYOX8 and the thumbnail quality is very good.

But once embed in my website: https://www.dimomaint.com/mx-connectors/erp-sage-business-cloud-x3/ the image is blurry.

Why ?

Your plugin use this image: https://i.ytimg.com/vi/21rmUNaYOX8/hqdefault.jpg wich is very little (640×360 px) compare to the one I gave to YouTube (1280x720px).

—
The settings of your plugin are:
– Your YouTube API key: “API seems OK, you can Save Changes below now.”
– Cache thumbnails locally? : NO
– Player size: 853X480 (Larger 16:9 player)
– Also act on normal YouTube links and iframes?: YES

Thank you.