It was standard for the charges they slapped on him but they didn't charge him in relation to the injuries suffered by the young girl. Judging from the reports, they could have easily went down the GBH path.
Could be wrong, but I believe that was only in the initial reports, and the only source for a broken hip was the girl's mum, mentioned in this article from October 2024:
The footballer’s manager said Mam was experiencing “personal challenges” but the family left injured in the crash said he should be held to a higher standard.
www.smh.com.au
This article from December 2024, largely criticising Mam, says 'minor injuries' which would be more consistent with the charges:
Mam pleaded guilty to driving with a relevant drug in his blood and driving without a licence in Brisbane magistrates court on Monday
www.theguardian.com
A four-year-old girl travelling in the other vehicle suffered minor injuries in the smash.
Magistrate Nolan yesterday reprimanded Mam for his “stupid decision” to drive.
He said the Bronco was “fortunate to stand where you are today given you were involved in a two-vehicle motor accident”.
“You could’ve been injured or killed or the other parties could’ve been injured or killed.
and similarly, from December 2024
https://www.abc.net.au/news/2024-12-16/brisbane-broncos-ezra-mam-fronts-court/104729554
Two people in the car, a child and a woman, suffered minor injuries.
Both articles after Mam had been to court and the facts presented.
That being said, there is no argument that it could have been a lot worse. Mam was very lucky in all regards and got off very lightly both in court (due to laws) and from the NRL.