A bishop could be married; it’s not an absolute impediment
The Scripture passage in question is not setting up requirements for bishops in the sense that a man chosen to be a Bishop must be married. If that were the case, St. Paul himself could never have been a bishop. What this passage is saying is that a man chosen to be a bishop should not have been married more than once. The fact that the word once is used shows clearly that passage is about limiting something rather than requiring.
Furthermore, to take this passage as literal requirements would mean a candidate for bishop must not only be a father but must also have more than one child, since the passage also says he must keep his “children” (plural) under control. Do you think that a bishop must be then father to at least 2 children, otherwise should not be a bish?
See!
I told you that you didn't know the meaning of MUST!!!
--Wannabe_Catholic_Dude("Hail Mary!", he replied haughtily.)