Why aren't my images showing up in the README.md file on NuGet.org

I have published a NuGet package with a README.md file in it. The README is displayed normally but without images.

How NuGet.org shows pictures

In F12 it looks like that:

F12 Description

I am aware that NuGet.org only allows images from trusted sources. Therefore the images are stored on a public GitHub repository.

I can see the images when editing them in VS code.

Image Link in VS Code

Also it is not an error while packing the nuspec.

Thanks for your help.

-Simon