Naruto's mom was a jinchuriki and he was conceived alongside 9T chakra. Plus he was born with whiskers. That implies that part of him is 9T allowing Kurama to embody him. Or it could be because Minato was already dead when he became a jinchuriki. Naruto is also just a way higher skilled jinchuriki than Minato.If Kurama had that power, why didn't Kurama allow Minato to use that power. I mean Minato can't die since he is already a Edo Tensei. A Edo Tensei can do everything a living ninja can do except use fake Rinnengan to its full power.
Kurama may have been getting more powerful over time and Naruto is no longer capable of sustaining the full power of the 9T without destroying his body.Just waiting for it be explained before labeling it an asspull but even still begs the question why he didnt use it earlier kind of seems theres a big cost to it and maybe kurama has to do prep for it