Unfortunately, it was Saruman's extensive knowledge of the Rings of Power that was one of the reason leading to his downfall, as he became enamored of the power of the rings, and particularly the One Ring.

Why did Saruman turn bad?

Paul Kocher identifies Saruman's use of a palantír, a seeing-stone, as the immediate cause of his downfall, but also suggests that through his study of "the arts of the enemy", Saruman was drawn into imitation of Sauron.

When did Saruman turned evil?

He [Saruman] becomes a traitor to the Council. I hope this sheds some light on the matter........it seems that it was around year 2851 that Saruman really began to lust for the Ring. Then he really became evil when he used the palantir and became a traitor ot the Council.