GNU Social was alive and well for the longest time. It previously was created out of older projects. There were some spin offs, but all were compatible and all server software got along. Then one day a 20-something year old twitter user wanted to make his own server software to replace twitter. He thought GNU Social wasn't good enough for his purposes so he asked for help to develop a new software suite. His name was Gargon.
Gargon had never programmed anything in his life, but this did not stop him. The GNU Social developers thought "Oh, nice! More people to help grow the Fediverse!" So they helped him develop the prototype to Mastadon.
Then, after the Prototype was fine enough, he decided to make some tweaks of his own. These tweaks made the network buggy. He didn't fret!
This was a good thing! It meant people would have to use Mastadon! But then, after he deployed Mastadon no one wanted to use it. Gargon was sad.
Then he remembered how fast things get latched on when a certian group of harpies and sirens promote it! He got the courageous Zoe Quinn to promote it! Mastadon was saved!
Eventually, the people that these harpies and sirens got to use his network discovered that the people who were already on the Fediverse were evil and vile. Some were trump supporters, and others didn't check their privledge!
So in order to save humanity, they decided to block entire servers rather than individual users. With that, the GNU Social software was even more buggy and slow.
Gargon was not finished with his crusade. He paid to have news articles written about his "New software" and his "New network". "Courageous day, I'm famous" thought Gargon!
At last, GNU Social has now died due to it's incompatiblity with the growing Mastadon network.