Release
Maybe. I mean - I honestly don't know how deeply the club is intertwined with modern day politics, and how all of that could eventually force their hand to make concessions of that nature, for potential sustainment revenues long term. Maybe there was a closed-door meeting with officials from the R&A and were informed that should they want to maintain a place in the Open Championship rota, they needed make a change to their male-only policy.
Or... maybe the old geezers with all of the old money are becoming fewer and fewer, and the younger influential members who tend to be a little more openminded than their predecessors are trying to soften the elitist nature there just enough to give the appearance that they're embracing typical cultural norms.
But yeah, at the end of the day it probably was a decision made more for financial reasons than anything else.