Postulates are not evidence.

Evidence is a contradiction or correspondence with postulates.

F.e. there is theory with postulate that some viruse cause some disease.

This postulate proves nothing and not evidence of anything. This postulate should be checked against reality. If every time somebody get a virus and become ill with that disease, than postulate is correct. If somebody have virus but doesn't get ill, then postulate is wrong and whole theory based on that postulate should be discarded.

Moreover, Koch's postulates is not about existence or non-existence of anything. They are about if some pathogen really a cause of some illness or not. Really any pathogen - poison, bacteria, virus, physical impact, whatever.

Viruses are pretty real, their existence was proven since tobacco mosaic virus study. In that study, every single time when isolated pathogen was introduced into the plant, plant always become ill.

However, today nobody even bother to prove connection between specific virus and specific illness arbitrary attributed to it. There are no any single scientific proof that influenza virus is a cause of flu or HIV is a cause of AIDS. Not a single one. Not even talking about coronahoax, where even existence of SARS-CoV-2 was never proven.

Medicine, instead of becoming hardcore natural science, with hard proofs and mathematically correct theories, like physics, chemistry and like, turned into complete anti-scientific bullshit at the level of astrology or sociology. There are tons of reasons for that turn, and all of them are malicious.