Massachusetts never enacted any laws against slavery."
In fact, according to this source, Massachusetts was the first state to free all its slaves, in 1783, through a Massachusetts Supreme Court decision, enforcing the 1780 Massachusetts constitution.
And of course you do not grasp the distinction between passing a "law", and a court riding roughshod over the law. Ladyjane is correct. Massachusetts didn't pass a law, They simply had liberal judges overturn what was then existing law.
Liberal Massachusetts has seemingly always had a penchant for Judicial Activism, and generally cares little what the law actually means.
Let's try an analogy: when was there ever a law against gay "marriage"?
Never, because it was always understood that marriage was between a man & woman, no other laws necessary.
Likewise, once the Massachusetts Supreme Court ruled their Constitution made slavery illegal, no further laws were considered necessary.
So I don't "get" why you think this is a big deal.
After the Declaration of Independence in 1776, Vermont was the first state to take action against slavery, in 1777, and Massachusetts the second, in 1783.
Yes, it appears that no Northern state abolished slavery overnight, but certainly by 1860 slavery was pretty much just a bad memory in all Northern states.
And your problem with this is what, exactly?