With very few exceptions, anyone can be elected to the committee – owner, tenant or even non-resident, non-owner – provided they are nominated by a ‘financial’ owner who is not running for office themselves (or is a sole owner who self-nominates).
In NSW a tenant could be nominated by an owner and be elected ahead of an owner who doesn’t have the support of the majority of owners.
However, if this is in NSW, there are several discrepancies with this process as you describe it.
Firstly, tenants may not nominate themselves – they have to be nominated by an owner who is not standing for election.
Secondly, there is a very specific procedure for the committee elections which has not been followed in this case.
Have a look at sections 9 and 10 of the Strata Regulations and Sections 29-32 of the strata Act.
If the strata manager has allowed a tenant to nominate themselves, and then allowed a secret, unsupervised ballot that doesn’t follow the Regulations, they really need to go back to Strata Manager School.
If what you say is correct in every detail, the strata manager should declare the election of the tenant invalid and should replace them with the ousted owner as the next valid nominee.