In the case of Berkeley (and San Francisco, also a premier GOP bastion for a long time -- which still had a GOP Mayor into the 1960s), yes. MA declined but made a comeback in the '80s and '90s. Weld and *omney destroyed the last shreds of competitiveness... and deliberately so.
I would counter that Weld and Romney (and Celucci) were the only types of Republicans that were going to get elected. In 1972, years before Weld or Romney stepped onto the scene, MA was the only state to vote for McGovern. It’s a lot more complex than can be explained but it’s decline has less to do with Romney and Weld than with issues such as demographic change and the Kennedy realignment. How would one explain Vermont then, which was easily more of a GOP bastion than MA ever even in its glory days was?