That is not the point. The present economic and monetary systems are ridiculously unsustainable and based on nothing tangible. What they are trying to do is collapse the system to force governmemnts and bankers to come up with something more sustainable and sensible. Revolutions doesn't always have to involve bloodshed.
This project helps prop up the current system. It doesn't hurt it in any way.
All of those donors just made people who trade in the secondary debt market 400k richer.
At the price they paid for that debt, clearly the company selling the debt had little to no expectation that the debt would ever be paid off. The Rolling Jubilee people were probably more than happy to let the seller pile mountains of complete junk that was just going to be written off into the package because it would make their stats look better.
The people who owed the debt were never going to pay it off, so they are not really practically better off. It is just the finance guys who profit off this.
If the organization grows, it will just pump more and more money into the hands of the financial guys who operate in this market.