Mealy Bugs

There is really no ’cause’ such as you describe for mealy bugs. They are common and ubiquitous insects on a wide array of plants. They do like the new, succulent growth that is often associated with house plants, but honestly, they can be found anywhere.
Stay vigilant, treat the ones you see to prevent or at least minimize the next generation. You can wipe them off with a soft damp cloth or dab them with q-tips dipped in denatured alcohol available at your local pharmacy, then wash off with water. If the infestation is persistent there are commercial sprays available at garden centers for this, but confirm the problem with a horticulturist at your local garden center and follow their recommended control. Usually the label will call for 3 sprays made 8 days apart to break up the life cycle, but make sure it is formulated for your plant.
If these aren’t mealy bugs they could be cottony scales, which are more broadly attached at the base than mealy bugs. There are treatments for them too. In either case, be certain the product is labeled for your plant group and use as directed.