The black sun bubble was some kind of force cavity of energy of some kind that is attracted to the sun, but it was getting filled with coronal energy except for the center of it, which could no longer hold the connection due to the buildup of coronal energy in the rest of it so the whole thing got shot off like a massive planet sized hot air balloon on steroids.

It may actually be the energy phenomenon that causes the larger ejections to occur in general.

I think they may be directly related to sunspots.

"A common and compelling feature of
white-light CMEs is their three-part morphology of a bright expanding loop, followed by a
relatively dark cavity, and lastly a bright core associated with an erupting prominence. It is
also quite common for a prominence with a dark, semi-circular or circular cavity surrounding
it to exist quiescently in the corona prior to the eruption. Multiple cases have been docu-
mented where the cavity and its enclosed prominence bodily erupt as CMEs (e.g. Figure 1).
Coronal prominence cavities are thus clues to the state of the corona just prior to a CME,
and may in fact be a signature of stored magnetic energy capable of driving the CME." [link to www.issibern.ch]