Considering the fates of atheists living around the time of Newton:
Wiki: "How dangerous it was to be accused of being an atheist at this time is illustrated by the examples of Étienne Dolet, who was strangled and burned in 1546, and Giulio Cesare Vanini, who received a similar fate in 1619. In 1689 the Polish nobleman Kazimierz Łyszczyński, who had denied the existence of God in his philosophical treatise De non-existentia Dei, was imprisoned unlawfully; despite Warsaw Confederation tradition and King Sobieski's intercession, Łyszczyński was condemned to death for atheism and beheaded in Warsaw after his tongue was pulled out with a burning iron and his hands slowly burned."
Not much motive for admitting a lack of belief in a deity!
Wiki: "How dangerous it was to be accused of being an atheist at this time is illustrated by the examples of Étienne Dolet, who was strangled and burned in 1546, and Giulio Cesare Vanini, who received a similar fate in 1619. In 1689 the Polish nobleman Kazimierz Łyszczyński, who had denied the existence of God in his philosophical treatise De non-existentia Dei, was imprisoned unlawfully; despite Warsaw Confederation tradition and King Sobieski's intercession, Łyszczyński was condemned to death for atheism and beheaded in Warsaw after his tongue was pulled out with a burning iron and his hands slowly burned."
Not much motive for admitting a lack of belief in a deity!
God thinks it's fun to confuse primates. Larsen's God!