I don’t have anything to add technically and there may still be a technical solution to the issue, but on first read I thought the increased humidity could be affecting the signal, but it might be that when it’s rainy more people are inside and streaming and contributing to the total load of the network.
Doom.
It was the first 3(well, 2.5)D shooter. Plus, I can hear E1M1.
And using the shareware license for distribution widely helped it’s popularity and it had multiplayer.
Honorary mention to Carrier Command ( the first one with like a 5 polygon island and a 40 polygon volcano).