I actually just read an article related
to this very question. In the mid-1800s America
was in a time of possibility, independence
had been won and black Americans were on
the verge of getting citizenship.
felt it was an appropriate time to ask for
more, and to be included in this newly shaped
country. Of course, the declaration also
was a response to their invisibility, their
rights weren't being prioritized. Though
they thought they were asking for "a
lot", I think they envisioned the battle
being easier than it was.
I hope that helps,
and for more read the last issue of Women's
Review of Books where there was a great article
by Vivian Gornick.