Bethesda has voiced deep admiration for Obsidian, the studio behind Fallout: New Vegas. Though rumors hinted at a rivalry, there is no real conflict between the companies.
In an interview with PC Gamer, Howard explained that Bethesda was the one who invited Obsidian to make the game after Fallout 3:
When we started work on New Vegas, we had just finished Fallout 3 and were already planning Skyrim. We know the team at Obsidian well — we admire their work — so we reached out and said, “Hey, would you like to take this on? We saw a chance to create something new after Fallout 3.”
When asked about players sometimes favoring New Vegas over Fallout 3 or 4, Howard responded:
That was the brief we gave them, and they delivered an exceptional job.
The rumors about a dispute originated from a contract bonus: Obsidian stood to receive a substantial payment if New Vegas scored an 85 on Metacritic, but the game earned an 84, so the bonus was not paid.
Source: iXBT.games