Why is it important that a historian considers people's perspective and biases; evidence; trustworthiness before they formulate their historical perspective?

It's important because they do not want to teach disinformation, misinformation, or just plain out lies. Here's an example, let's say a historian was asking a co.vid denier if co.vid is real, and if that historian didn't know any better then they will write that down and boom history.

Explanation:

This should be common sense not just for historians.

but whats the question? ?

explanation:

which statement explains one of the reasons world war 1 was so much more destructive than earlier conflicts