It's the right move for UMass.
UMass has a better shot of winning games and being competitive in basketball in the MAC than they did in the A-10. Fans weren't coming out to the hoops games because they might see a VCU team that went to a final four a decade ago, they were going to the basketball game and hoping to see a win. Seeing a few more wins will mean a few more people. The high attendance last year was 5000 on alumni day, with a free jersey giveaway, overall they averaged just over 2800 (and it was pretty consistent between 2500-3000 per). There was nothing left to protect for them in the A-10.
They simplify football scheduling and should have a more manageable schedule, who knows with a few wins there maybe they manage a few more fans there... if nothing else they will make more in overall revenue from conference distributions (media rights, football playoff & tournament distributions). The A-10 media revenue reportedly was around 525k per school on the new deal. The MACs previous deal (signed in 2014) would pay between 667k and 800k per school (based on reported escalators), with a negotiation expected to yield an increase from the 2026-27 season (for context the A-10s new deal was a 40% increase on their previous deal signed 4 years prior).