Yuta's VA Megumi Ogata: The Director and the rest of the team decided that if they handled it like a "normal" anime and spread it over two episodes, the combat would lose its momentum. You’d end up with scenes of characters just staring each other down or standing with their arms crossed. They felt that wouldn't fit the Jujutsu Kaisen style. They wanted the combat to feel relentless, like a non-stop battle.
Source: JJK Anime VA Podcast
Translation: @BocchiTheCrock2