Video Block useless preview image

I have built a page that I structured with @eeacms/volto-columns-block and volto-subblocks. In this design, a video block is embedded in a column. This video block contains both a local video file and a locally saved preview image.
I would actually assume that if a preview image is specified, it will be displayed when the page is accessed. Now there are 5 videos embedded on the page and when the page is accessed the videos are still loaded so that the page only responds again when this is finished with loading.
Can anyone understand this behavior or can this behavior be changed with a configuration?

It's a problem with the Embed component from semantic-ui-react, it needs to be fixed.

Thank you for the tip, do you think it is possible to create a personal css class as a workaround?