As Jer 41 records the infamous treachery of Ishmael, so Jer 42records the obstinate disobedience of Johanan. These incidents are recorded (instead of many others) because they show us something of the moral character of the People; and thus furnish us with the reasons for the calamities which overtook them.
Jezaniah. In Jer_43:2 he has a second name, "Azariah". The Septuagint reads this name here.