I agree with all that Kaindub has said. If all powers have been delegated to the strata manager then you have to take them back if the SM isn’t even doing the basics.
I would compile a document prior to your next AGM that explains to owners how the value of their investments is being eroded by neglect of the building. Compare like-for-like rents with nearby blocks that are well-maintained. The one thing that motivates investor owners above anything else is money.
And then there’s the argument that if the committee isn’t even going to trouble themselves by having a chair, and secretary, then why are they even standing for election?
Get the email addresses of all the owners and start your campaign. The strata manager may refuse to give you the email addresses on the entirely spurious basis of privacy. This is nonsense. You are entitled to see all records of the Owners Corp and that includes email addresses.
And as far as taking back the offices of the committee, all the committee has to do is meet, pass a resolution and inform the strata manager. So, as Kaindub says, take over the committee with at least one committed and organised person by your side, and off you go.