Good question.
The march organizers may be more concerned about losing what rights the GLBT community may lose with a president who doesn't care about GLBT people one way or another but would be quite willing to throw them under the bus if it gets his economic agenda passed, a Republican Congress dominated by social conservatives who want people to have the "religious freedom" to discriminate against GLBT people, and a Supreme Court which is one or two Trump appointees away from using the same logic that would overturn Roe v Wade to overturn its Obergefell same-sex marriage decision and other GLBT equality court cases.
Sure, it's speculation.
But, conservatives spent eight years rallying behind speculation about Obama.
And I repeat:
GLBT people simply want the same rights you already enjoy.