Why does the download / upload speed on cloud services sag when using the Internet over a radio channel?

Question

Data storage

Dear IT specialists, tell me! I connected Internet services, via a radio channel, I previously used it via optics, the speed according to speed tests is stable, but the speed of downloading / uploading files on cloud services sags. When using the Internet via optics, the speed of downloading / uploading files is stable. Tell me why is that?
I will be grateful for the answer.
Thank you!