Ask HN: Projector and DRM?

I have been using Firefox with my Epson projector to watch legally purchased movies from Amazon Prime Video, Disney Plus, Hulu, etc. After what I suppose is a recent update, the DRM has caused my movies to just display as a gray screen with sound only. This happened before on Safari but never on Firefox. I was able to plug the projector into an HDMI and get it to work, as opposed to watching it wirelessly over the projector's WiFi casting capability. Why is this legitimate use case being blocked by DRM?