(also known as: fallacy of insignificant, genuine but insignificant cause)
Description: An explanation that posits one minor factor, out of several that contributed, as its sole cause. This fallacy also occurs when an explanation is requested, and the one that is given is not sufficient to entirely explain the incident yet it is passed off as if it is sufficient.
Factors A, B, and C caused X.
Factor A, the least significant factor, is said to have caused X.
Billy murdered all those people because I spanked him when he was a child.
Explanation: Assuming that spanking did contribute to Billy's murderous behavior as an adult (which is a very weak assumption), to sell that as the cause is extremely fallacious.
The reason Donald Trump got elected was because liberals took political correctness too far.
Explanation: Assuming liberals did take political correctness too far, and this did have some effect on voters in favor of Donald Trump, it is unreasonable to claim that this was "the reason" for his win.