Why don't you tell me.
The fact is I don't know. (Take a peek at my tagline).
I do know they weren't appointed by a non-existant Pope.
If you suggest the Apostles appointed Bishops then you agree there was no central (Pope) appointing authority.
If Paul appointed Bishops was he the Pope?
I made no claim that things in the RCC have remained unchanged for 2,000 years. You found it necessary to answer for someone else so I assumed you had facts, not smoke, to back your claim.