Let us be clear on this point. Your claim is only valid if you have evidence of it prior to the Declaration of Independence. What they did subsequent to 1776, (The year they actually established the new government) is irrelevant to what was their intent when they established the new government.
You can't justify past actions by claiming future actions made your past actions right.
So do you have any example of the founders great concern over slavery prior to 1776?
Looking at your link, the answer would appear to be "no."
So let's be clear on this point. *WHEN* the founders were actually creating the new government, they did not give a crap about the issue of slavery. As a matter of fact, they forced Jefferson to remove some of his abuses from the Declaration of Independence that cast slavery in a bad light.
Remaining in the Declaration is an actually pro-slavery statement. "He has incited domestic insurrections among us..." meaning slave revolts.
They considered offering freedom to the slaves to be an "abuse" by the British Crown.
Let me turn that on it’s head.
How about you show me the philosophical turning point that happened prior to the Declaration of Independence and the Federalist Papers to turn our forefathers that you think supported slavery to what they said after 1776.
For context, here’s some of what was written in the Federalist Papers on slavery:
https://vindicatingthefounders.com/library/federalist54.html