Anastasios,
Then Bishop Chrysostomos was "walled off", in the legitimate sense of the term, with two other bishops precisly because of the upheavals you mention in that time. They did not start alternate synods or make any other moves against the synod - they simply wanted to be isolated from the turmoil.
He was not "installed out of the blue". Maybe in the limited few sentences you have read which are used to describe these complex events it may seem "out of the blue". Bishop Petros was one of the bishops walled off, and they kept very close contact with the synod during this troublesome time. Bishop Chrysostomos was elected archbishop because he was recognized as somebody who was worthy of that position and could help straighten things out. And he did with the help of the Lord.
The fact that Auxentios's renegade "synod" did ordain a known homosexual to be "bishop", that those three bishops came to nothing, and that none of them appeared before the Holy Synod to answer of the chages against them is proof enough against any idea that they were legitimate after that point.
But this thread is not titled, "What is wrong with the 'Florenites' " ( you can start that if you like), so I would like to point out that you have not addressed my point.