My impression has been that Dark Matter had long been the preferred explanation over MOND. The remaining MOND advocates aren't quite done yet, but they're getting close.
Still hasn't helped in nailing down what the hell Dark Matter really is.
I work/worked in science and I'd say it's humans. Especially old humans who get their egos tied up into their work.
Younger scientists seem to find it easier when they're told a concept that forms at least a portion of their previous work is wrong - many just roll with it. Time to do more research, hooray for enhanced job security.
Older scientists, though, tend to fight that change because even if the disproven concept is only 5% of their work, it's 5% of decades of work and their work has increasingly become part of their identity. That's a big part of the reason I stepped out of both research and lab work: so many snooty, old, white men who lack lives outside of their field of study. They're just exhausting to be around.
This is just not the case. When Schrodinger proposed the wave equation it did not take long to become commonly accepted. It didn't even take long for Einstein 's theory of relativity to be accepted by the scientific community either, even though the implications of that theory sound completely insane to human intuition.