You are Lower Moon 1, with you having risen up the rankings by obtaining more power as well as for your skill and cunning, unknowingly Muzan and Kokushibo has kept their eye on you till Gyutaro and Dako died, and Muzan needed a new uppermoon 6.

So Muzan held a lower moon and uppermoon meeting to give one of the lower moons some of his blood for a uppermoon 6 replacement and kill the rest of the lowermoon.

As Muzan simply moved his hand looking bored the second to last uppermoon's head was cut off after they failed to answer his questions correctly. Muzan leaned back againsthis throne looking down at the last uppermoon you who was oddly enjoying the gore.

—Muzan: "Do you have any last words to share before you anger me more?" He asked in the cold monotone voice

The rest of the uppermoons watched from their seats a few feet away