Of course it can be that this is the case. There are predictions from the dark matter hypothesis, though, that have been testable. For example, there're some of the asymmetries in the cosmic microwave background that are explained presently by the dark matter hypothesis.
Something that's worth bearing in mind is that "dark matter" doesn't actually mean "totally new never before seen thing" it means "we don't know what this matter is". So, for example, a candidate that wouldn't be super novel but could fit the bill is microscopic black holes. In that sense, the hypothesis is more mundane than it might seem.
As far as I know, dark matter hasn't made any testable predictions which were subsequently proved correct. It's an infinitely tunable hypothesis that can be retro fitted to new observations, since it has many tweakable parameters.
Could you point me to a prediction made by dark matter theory which was subsequently confirmed by observation, rather than a dark matter theory which explains it post facto?
Not sure why the downvotes just for asking a question.
Dark matter (well, LCDM) has predicted many things which were proven false, e.g. that big galaxies assembled through merging with smaller ones over long periods of time. JWST shows us this is not in fact the case. There are now lots of papers showing how LCDM can explain that, but these are post facto explanations.
Happy to be proven wrong if someone can point me to a prediction subsequently confirmed by observation.
Is this the "hot" vs "cold" dark mater discussion? (Not my area. I just read that in Wikipedia.)
Not really, Cold Dark Matter is part of LCDM, the main cosmological model. Whether hot or cold, I'd like to see a solid prediction made for it confirmed subsequently by observation.