it has been known to happen.

For example, spearheaded by Knuth, the community effectively abandoned the Journal of Algorithms and replaced with with ACM Transactions on Algorithms.

however it's difficult. a big factor is that professors feel obligated towards their students, who need to get jobs. even if the subfield can shift to everybody publishing in a new journal, non-specialists making hiring decisions may not update for a few years which hurts students in the job market.