Wah, I hated the ending of Halo 4*. So, I decided to look at it in depth and I’ve come up with the following theory (it’s quite short).
Master Chief has been indoctrinated by the Didact. He didn’t even wake up from the initial crash that he suffered. He is essentially just dreaming about everything that is happening. Also, Didact made him imagine the ranking system isn’t visible so that’s why that happened. So, yeah, The Chief is indoctrinated. In Halo 5, the game will start from that very point where he wakes up revealing this. Sorry for spoiling it for you all.
*I actually loved the ending of Halo 4. 343 did an amazing job.