Definitely helped but not the full story. The entire biotech sector has been surging for 5-10 years, a combo of a build up of capital in the low-interest rate era and multiple quite highly promising new therapeutic approaches in several disease areas. A little less clear now that interest rates are actually a thing and investors care about things like turning a profit, but the fundamentals are likely pretty strong going forward.

It's not just Boston (and thus not the result of any state investment/initiative); all the traditional biotech hubs have had huge growth, though since some of this has been masked because some biotech hubs (Bay Area, Seattle) overlap with Tech hubs which have grown even more.