Youtube Video Listing Embedding Issue

CS Cart 4.2.1

When I embed a youtube video into the body of my product listings no matter how big I make the video size it comes out small within the web page listing… at 1280 X 720 from youtube its huge in my listing editor in the admin panel but small in the web page

Youtube code ----

I am using the built in TINYMCE WYSIWYG editor (the other built in ones are horrid)

The first sample picture attached is from my soon to be live site …On my site that I am building no matter how big I adjust the size of the youtube code to it only ever comes out at approxmatley 8.5cm long by 4cm high (rather small)

The second picture is from one of my other online listings on eBay and it shows up in the body of the listing at approxmatly 16cm long by 9cm high

So why the difference in cscart and how do I make the youtube video/s bigger in my actual listings within cscart?

Thank you in advance for your answers and input



Do you use custom theme? Or basic? Or responsive?