A little over 20% of Massachusetts deaths occurred before May 6th, 2020. Another 20% occurred in the 3-4 weeks immediately ofter which are likely largely attributable to people who got COVID before early May.

If you compare Massachusetts deaths after that point to other states they come out somewhere near the middle.

Did the mask mandates change in MA across these time ranges?

Not significantly, it came into force May 6th indoors and outside if you couldn't maintain 6', but most cities in eastern MA had 100% outdoor mandates too. I think it was Nov 6th when they made it 100% outdoor statewide regardless of distancing. The mask mandate wasn't lifted until May of this year.