“I never signed a contract giving Mojang the rights to the End Poem, and so Microsoft (who bought Minecraft from Mojang) also don’t own it.”
Microsoft paid $2.5 billion for Minecraft and never checked who owned the ending. The writer got €20,000 on a handshake, and the contract showed up a month after the game shipped. He never signed it. So he gave the poem to the public domain. That’s a better deal for the players than anything Microsoft ever offered him.