Oda had them change their minds for the readers.
If, the Gorosei protected York from the get-go, CP0 would not get the order to kill all Vegapunks, which would lead us to figure out the mystery and know from the jump that it's York.
The mystery mini-arc was more important to Oda than the narrative consistency.
Also, the Gorosei are known to be incompetent, so this is in line with their character. Indecisiveness, incompetence, impatience, over-panicking, rash decisions, etc.. I just wonder how Oda was able to sell us that these Jokers were able to rule the World for 800 years
If, the Gorosei protected York from the get-go, CP0 would not get the order to kill all Vegapunks, which would lead us to figure out the mystery and know from the jump that it's York.
The mystery mini-arc was more important to Oda than the narrative consistency.
Also, the Gorosei are known to be incompetent, so this is in line with their character. Indecisiveness, incompetence, impatience, over-panicking, rash decisions, etc.. I just wonder how Oda was able to sell us that these Jokers were able to rule the World for 800 years