dust isn't mold... it would require damp, dark & cool to become mold in time.

Attics are typically dry, dark & hot... mold doesn't survive in those conditions.

So much dust... attics are typically dirty areas due to most of them being naturally vented. During storms and such dust and dirt is kicked up in the air drawn in thru eaves or gables in the roof then once in side the attic the dust and dirt settles on everything. Over the passing of time it builds up to look like what you see here. (This old house story)

Another possible contributor is poor dryer vent exhaust or broken dryer vent exhaust that spews lint into the attic every time some one does the laundry. That can be a fire hazzard so look to see where dryer vent is vented to. (it shouldn't be vented to the attic)

The house looks old (from what you show)... so nothing really jumping out as out of the norm for an old house. Attics are always dusty and dirty, not so much in a new home but that's why it is new.

It could also be insulated with loose fill cellulose which can get blown around in heavy wind. Other than checking that the dryer and baths are vented properly nothing looks unusual

"dust isn't mold... it would require damp, dark & cool to become mold in time." For mold to grow it requires 1.) a food source, 2.) water, 3.) an appropriate oxygen level, and 4.) suitable temperature conditions. Some molds can grow at 86F which I don't consider to be "cool." Nor do they need the environment to be "dark." While they can survive in dark environments because they do not utilize photosynthesis, "dark" is not a requirement for them to grow.

"Attics are typically dry, dark & hot... mold doesn't survive in those conditions." Generalizations can get you into trouble. The conditions in an attic will vary depending on the details of the home's construction, the amount of ventilation, the climate zone, and the time of year. Attics in heating climates can have winter condensation problems which can lead to mold/mildew growth when spring temperatures arrive. For this reason, attic conditions should be evaluated on a case-by-case basis.

Blown cellulose gets everywhere, and clings to everything. Holding on to the end of the hose and directing it can be a homeowner job, but then you can get scenarios like that, where the control level just wasn't there, and they blew it everywhere. None of that is dangerous, or even remarkable. Just sloppy. I'd want an inspection from an Energy Rater, to see if the existing insulation was adequate, and maybe needed augmenting. Your local utility company probably has names to give you for that service, and it is often free, or highly subsidized by them.