In an interview with The Gamer, Fallout 2 designer John Deiley spoke about the reasons why it was decided to destroy the sentient Deathclaws. Initially, they could appear in future games in the series.
Let us recall that in Fallout 2, the Chosen One could meet intelligent Deathclaws in Vault 13. The creatures were bred by the Enclave and had the intelligence of an eight-year-old child, but did not attack the protagonist. Later in the story, the entire colony is destroyed by the Enclave.
According to John Daly, these creatures could appear in future games. Deathclaws would become significantly smarter thanks to the use of FEV (man-made evolution virus), and would also wear their own power armor. Players may have encountered them while exploring the Wasteland. The monsters would be «smart but still aggressive», so some encounters would end with a fight with them.
As the designer said, Chris Avellone really didn't like the idea, and he decided to get rid of the intelligent Deathclaws, writing their destruction into the game's lore. The game designer considered the idea too «stupid» for the series.
One day I was walking down the hallway and I saw Fergus in one of the programmer's offices and I saw the screen over the programmer's shoulder and it was [Vault 13]. I went in there and I said, 'What's going on?' [They said,] «Oh, well, we've decided to eliminate this area from the game. But we don't want to just not include it. So, the Enclave is going to kill them all off».
The designer did not challenge this decision, explaining that «going against Avellone's ideas was the end of his career.»
Let's remember that we recently talked about the reasons why a player destroyed Phil Spencer's hideout in Fallout 76.