A lot of the confusion comes from us applying our everyday concepts like 'particle' or 'wave' and giving them an absolute, real meaning.

A good (though imperfect) way to think about it is a water surface: Is it a wave or individual droplets? The question isn't really answerable until you measure it. The moment you put an object into it, a droplet sticks to it—you've made a measurement. The previous superposition of possibilities (wave/droplet) has 'collapsed' into a single, concrete result (one droplet).

The crucial point that goes beyond the water analogy is that the mathematics describing this 'fuzziness' (the Schrödinger equation) is ultimately a probability calculation. It's a tool for our knowledge about the system (epistemic), not necessarily an exact description of a physical vibrating process. What happens 'in reality' before we measure is the subject of various interpretations of quantum mechanics. The most common one (the Copenhagen Interpretation) indeed says that the measurement itself brings about a definite state.

It's common for folk with idealist tendencies to confuse what they believe, understand, think etc. with what is true. — Banno

What you're saying perchance isn't just that pseudo idealists (those with idealist tendencies) confuse the mental as the only real, but it's that's true idealists are confused because they think the mental is the only real.

In other words, true idealists are being true to their worldview. It's not as if they're realists but have illogically assessed the consequences of representationalism to mean there is no ontological truth (as a pseudo idealist might).

As in, Berkeley is logically consistent and Kant allows a distinction between the unknowable noumena (the ontologically real) and the phenomena (the mentally known). Those folks aren't muddling epistemology with ontology.