Pope Francis appointed Pell to reform the Vatican's financial affairs in 2014 as head of the newly created Secretariat for the Economy.
Becciu, who reportedly clashed repeatedly with Pell over the Vatican's financial reforms, was fired after Pope Francis accused him of embezzlement and nepotism.
In a statement to CNA on Sept. 25, Pell wrote that the Pope "plays a long game" and should be "thanked and congratulated" for asking Beccui to resign.
"The Holy Father was elected to clean up Vatican finances," Pell wrote, adding that he hoped the "cleaning of the stables continues in both the Vatican and Victoria."
Cardinal Pell and Cardinal Becciu were reportedly previously at odds over reform of the Vatican's accounts.
In 2015, Pell reportedly detected an attempt by Becciu to disguise loans on Vatican balance sheets in an accounting move prohibited by the Pope in 2014.
Becciu also cancelled, without permission from the Pope, an independent external audit of all Vatican departments initiated by Pell, who as head of the Secretariat of Economy had autonomous oversight authority over Vatican finances.
The former Vatican treasurer "always intended to return to Rome," said Katrina Lee, an adviser to the Archdiocese of Sydney.
Pell took leave from his position as head of the Vatican's financial affairs in 2014 when Victoria police brought sexual abuse charges against him, and he returned to Australia to fight the charges.
Pell was acquitted in April by the High Court of Australia after serving 13 months in solitary confinement. He will reportedly return to the Vatican on Sept. 29 after living in Sydney.