> ruling party replaced not only the extraneous judges, but also those judges who were lawfully supposed to be appointed by previous government
The problem is that previous government broke the law in more than one way:
1. They appointed more judges that they were allowed to.
2. They did appoint all those judges by means of single parliamentary resolution, despite the fact that Polish Constitution clearly requires voting for each judge separately.
Given those two points NONE of the judges was appointed lawfully, and there was no other way forward than repeal the whole resolution, therefore removing all 5 unlawfully appointed judges.
> and there was no other way forward than repeal the whole resolution
That's not what happened though. The Constitutional Court ruling[1] deemed the appointment of three judges constitutional, and two of them unconstitutional - and, according to the Constitution, those rulings are final, immutable and to be immediately published. However, president Duda didn't swear any of the new judges, despite of being legally obliged to (the president doesn't have the right to decide whether the judges were appointed legally or not, it's the Constitutional Court's job) and once PiS appointed five new judges (instead of two they were legally able to) the president swore them all.
Uh, whose interpretation is that? Constitutional tribunal ruled itself that three judges were correctly appointed by previous parliament. (case K34/15)
The problem is that previous government broke the law in more than one way:
1. They appointed more judges that they were allowed to.
2. They did appoint all those judges by means of single parliamentary resolution, despite the fact that Polish Constitution clearly requires voting for each judge separately.
Given those two points NONE of the judges was appointed lawfully, and there was no other way forward than repeal the whole resolution, therefore removing all 5 unlawfully appointed judges.