My internet is good and i have no problems with it but yesterday i noticed that when i open Minecraft launcher my network speed decreases 10 times to around 1MB per second. Websites like speedtest.net confirm that, also if i'm downloading something in steam and then open launcher i instantly see download speed slowing down and in task manager networg usage drops from 99% to 10-15%. Closing launcher instantly restores network. It did not happen a week ago

I tried:
Reinstalling MCL
Deleting .minecraft folder
Reinstalling Java
Deleting recent Windows update
Reseting IP configurations via PowerShell
Updating network adapter drivers
Switching from Ethernet to WLAN
Switching to different network (other wifi)
Restarting some services

Nothing helped and i culdn't find any information about that problem. I'm not sure what exactly is the problem, but after checking i'm pretty sure that my adapters and network is fine. I just know that having MCL open decreasing network usage on my PC.

Minecraft itself does NOT cause this problem, so it's possible to play on servers if you kill MCL via task manager.