You are correct that cardinals do profess an oath of faithful obedience to the Pope…
“I, _____, of the holy Roman Church, Cardinal of _____, promise and swear from this hour hence as long as I live to be faithful and obedient to the blessed St. Peter, the Holy Roman Apostolic Church, and the Most Holy Lord Pius X, and also his canonically elected successors.”
… but that obedience extends only to matters of Church doctrine and matters of faith.
"I swear to observe and fulfill and see that others observe and fulfill, the regulations, degrees, ordinances, dispensations, reservations, and provisions of the Apostolic mandates and constitutions of Sixtus First of happy memory, and to combat with every effort, heretics, schismatics, and rebellious utterances against our Lord the Pope, and his successors.
It does not bind the Cardinals to obedience in matters beyond the authority of the Pope. Cardinal Pell would in no way be obliged to take, for example, legal counsel on civil matters from the Pope. The Pope would be acting beyond his authority to order Cardinal Pell to take some legal recourse or other against the advice of his lawyers.
A parallel case would be a pope ordering a Cardinal to obey him in matters of medicine, for example. That is not in the realm of matters the Pope has any kind of authority to command a Cardinal or Bishop or Priest. A pope would not do that.
Neither would a Pope interfere with a Cardinal acting under the legal advice of lawyers in a civil or criminal matter. It just would not be in the jurisdiction of a Pope to expect that kind of obedience.
The Pope is neither a lawyer nor a physician, and would not pretend to be one. That kind of interference would not be defensible.