B Betelgeuse unusual dimming - what's up?

[Astronuc]

The scientists have concluded that some time before the great dimming, the star ejected a large gas bubble. When a patch of its surface cooled shortly afterwards, the temperature decrease was enough for heavier elements, such as silicon, that were contained within the gas to condense into solid particles.

This is an interesting piece that's not mentioned in other published summaries. I take the part about "before the great dimming, the star ejected a large gas bubble" to mean something like a CME, but it was still hot and transparent. Then "when a patch of its surface cooled shortly afterwards, the temperature decrease was enough for heavier elements, such as silicon, that were contained within the gas to condense into solid particles." But isn't it the ejected mass that cooled? Or did the outer surface cool?

In either event, cooling such that Si or perhaps SiO₂ precipitated and condensed into dust particles, and perhaps Al₂O₃, or alumina-silicates.

There is this paper "A dusty veil shading Betelgeuse during its Great Dimming"
https://www.nature.com/articles/s41586-021-03546-8