I feel like there is a neat science-fiction story in here somewhere :) A hyper-advanced space civilization embarks on a multi-million-year mission to tow black holes into neighboring galaxies in order to suppress star formation there and thus reduce the chances of competing civilization appearing in the next few billion years
It also would be more efficient to go to that galaxy, tow its stars around, and form new black holes there. You'd move much less mass a much shorter distance. You could probably even pick a relative handful of stars and just nudge them and wait; they're already moving after all. Might as well use that momentum.
Super advanced AI civilization spreads in all directions. Eventually the loyalty and purpose bits flip and the far-flung frontiers no longer share the same mission profile or allegiances.
As for the motivations of this civilization, I'm not sure, no one has written this story yet :)