IIRC they had an agreement that Globalfoundries were to take the fabs and further develop them to shrink to better nodes. I think it was less than a "take this crap off of us" and more of a "we still need fabs, so here's some money and please continue running them for a while". GloFo then utterly failed at competing with TSMC, Samsung and Intel which was quite a problem for IBM. In general if you have a certain design you can't immediately port it to a different fab, you need to engineer it around the constraints of the fab node and process