There was a step in between, SolarCity was in trouble so they issued SolarBonds. Musk and some of his companies, notably SpaceX, decided to buy these since ther

There was a step in between, SolarCity was in trouble so they issued SolarBonds. Musk and some of his companies, notably SpaceX, decided to buy these since there were not enough interest. So this final buyout was not to save SolarCity, but to save Musk and his companies that had previously rescued SolarCity.