Cardinal George Pell, page-212

Prosecution — Key arguments: Director of Public Prosecutions Kerri Judd QC, senior crown prosecutor Mark Gibson SC and crown prosecutor Angela Ellis.

● There were opportunities for Cardinal George Pell, newly installed as archbishop of Melbourne, to sexually abuse two choirboys in the late 1990s. Evidence that the boys slipped away unnoticed from the post-mass procession because of “mischief” and were “caught” by Pell while drinking wine in the priest’s sacristy — the room in a church where a priest prepares for a service — withstood defence arguments.
● Pell used the priest’s sacristy to vest and disrobe during Sunday mass because of renovations that rendered the Archbishop’s sacristy unusable. There were times Pell was left alone while still robed. It was still possible for Pell to expose his penis to the boys while robed because of slits in the alb, an under-tunic, which were designed to access pockets.
● Neither victim reported the abuse at the time but that does not mean it didn’t happen. Mr Gibson quoted the surviving complainant: it “took a courage much later in life” to even consider speaking out. He feared jeopardising his scholarship to the prestigious St Kevin’s College, making things difficult for his parents and struggling to understand what had happened and if it was “normal”.

Obviously, this is just a summary but the argument seems to be that the victims story is feasible rather than providing evidence that it actually occurred.  

So, it does appear at face value that is was one person's word against another.

My understanding is that Pell did not take the stand to defend himself.

So the jury believed the victim's story.