LBJ did some great things and he did some bad things. I can see that understanding and explaining how someone who had a life of immense consequence came to do both would be immensely valuable. That explanation could help drive the culture towards considering how we can get the former and avoid the latter as much as reasonably possible. If one was successful in that project, it is possible that their work would be more impactful in the long term than the person that they are writing about.

Also, some people are just compelled to do really deep work because they like it.