No, they just didn't speak out against christianity in those days.
At least not publically.
Jefferson spoke out about the Trinity several times:
"The hocus-pocus phantasm of a God like another Cerberus, with one body and three heads, had its birth and growth in the blood of thousands and thousands of martyrs." -- Letter to James Smith, December 8, 1822
And his thoughts on the Virgin Mary?
"And the day will come when the mystical generation of Jesus, by the supreme being as his father in the womb of a virgin will be classed with the fable of the generation of Minerva in the brain of Jupiter. But we may hope that the dawn of reason and freedom of thought in these United States will do away with all this artificial scaffolding, and restore to us the primitive and genuine doctrines of this the most venerated reformer of human errors." -- Jefferson's letter to John Adams, April 11 1823
And the ministers of the day called Jefferson an atheist and tried to block his presidency. That ministers claim him today is hypocrisy.
His views on religion were not those of a man of faith: "If by religion we are to understand sectarian dogmas, in which no two of them agree, then your exclamation on that hypothesis is just, "that this would be the best of all possible worlds, if there were no religion in it." But if the moral precepts, innate in man, and made a part of his physical constitution, as necessary for a social being, if the sublime doctrines of philanthropism and deism taught us by Jesus of Nazareth, in which all agree, constitute true religion, then, without it, this would be, as you again say, "something not fit to be named even, indeed, a hell." -- Letter from Thomas Jefferson to John Adams, May 5, 1817
And George Washington?? lol
""The father of this country was very private about his beliefs, but it is widely considered that he was a Deist like his colleagues. He was a Freemason."
Historian Barry Schwartz writes: "George Washington's practice of Christianity was limited and superficial because he was not himself a Christian... He repeatedly declined the church's sacraments. Never did he take communion, and when his wife, Martha, did, he waited for her outside the sanctuary... Even on his deathbed, Washington asked for no ritual, uttered no prayer to Christ, and expressed no wish to be attended by His representative." [New York Press, 1987, pp. 174-175] "
"Paul F. Boller states in is anthology on Washington: "There is no mention of Jesus Christ anywhere in his extensive correspondence." [Dallas: Southern Methodist University Press, 1963, pp. 14-15] "
Benjamin Franklin?
". . . Some books against Deism fell into my hands. . . It happened that they wrought an effect on my quite contrary to what was intended by them; for the arguments of the Deists, which were quoted to be refuted, appeared to me much stronger than the refutations; in short, I soon became a thorough Deist."
And in Poor Richard's Almanac he wrote "Lighthouses are more helpful than churches." and "The way to see by faith is to shut the eye of reason.".
http://freethought.mbdojo.com/foundingfathers.html