Why doesn't a website hosted at home offer the same download speed as just transferring files?

I am hosting a Django website at home on which I can watch specific video's and photos wherever I want. The only problem is that some of the video's take a while to load and keep buffering. Even when I am on the same wired network. When directly watching the video's from a shared network folder it all works fine. Transferring these video files from the network shared folder to my PC works at around 120 MB/S and speed-test online show me my network speed of around 250 MB/S so the internet speed shouldn't be the issue. But why am I not able to stream these video's properly from the Django web-page? When checking my network activity while watching a video from the network web-page it shows me around 1 MB/S which apparently isn't enough. Does anyone know I could fix or improve this?