Coincidental timing to the protest actions, or a natural event? Three aftershocks in the 3.x-4.x magnitude have occurred after the major tremor, per CSEM/EMSC.
-NW

M 5.9 - NEAR S.E. COAST OF AUSTRALIA - 2021-09-21 23:15:52 UTC
CSEM / EMSC
https://www.emsc-csem.org/Earthquake/earthquake.php?id=1039326#summary

Magnitude Mw 5.9
Region NEAR S.E. COAST OF AUSTRALIA
Date time 2021-09-21 23:15:52.2 UTC
Location 37.48 S ; 146.33 E
Depth 2 km

Distances
126 km ENE of Melbourne, Australia / pop: 4,246,000 / local time: 09:15:52.2 2021-09-22
38 km S of Mount Buller, Australia / pop: 2,500 / local time: 09:15:52.2 2021-09-22

Witness location : Mount Buller (Australia) (39 km N from epicenter)
Nothing fell over, but everything was shaking and I thought I had to leave my building

Witness location : Mansfield (Australia) (50 km NW from epicenter)
Whole house shook for 30 to 40 seconds with smaller shakes diminishing over the next 60 seconds