Was this because she shagged someone ?
No. It's more the (alleged) interventions in multi-million dollar (taxpayer-funded) grants with the guy (disgraced former member of parliament) she was shagging. The shagging itself is a non-issue.
https://www.abc.net.au/news/2021-08-09/gladys-berejiklian-daryl-maguire-grant-intervention-letter/100354146
Grant wise, similar to her coalition partners in federal government in relation to provision of grants, even if not as bad or level of corruption.
Morrison would not be in his job if they had real ministerial standards and plenty of others would also roll if there was a similar national ICAC.