How many closed-source, for profit software projects were rescued after the supporting company went under? (I am intentionally conflating closed-source and for profit as the majority of financed projects are closed source).

What you have to consider here is the rate of progress, as well as the length of development time. Open source projects have essentially infinite development time, whereas closed-source, for profit projects have a finite development time (whenever the company decides further development isn't worth it anymore)+. However, open source projects tend to have a slower rate of progress versus financed projects.

After 6 months or 1 year, sure, the financed project will probably be ahead. How about the 5 year mark? 10 year? It becomes much less clear which project will have accumulated more man-hours.

+very rarely, closed-source projects are released as open source (e.g. Doom 3), but I think we can all agree that that is the exception to the norm

Well, if we compare to the list in the parent, it's much more. At least Firefox, Blender, Rails qualify. These were products that had no future in closed-source form. If they had, it would have been financial madness to open source them.