Neither the good nor the true is self-realizing, so it is not generally a sufficient explanation of why people believe that X is true, or of why people do Y that Y is good.

Asking what the question is, and why the question is asked, is always asking a pertinent question.

Can one understand politics without understanding history, especially the history of political thought, and will this distinguish political philosophy from some other kinds of philosophy (such as, perhaps, logic) to which the study of history is not integral?

It is an assumption that there is always one single dimension for assessing persons and their actions that has canonical priority. This is the dimension of moral evaluation; "good/evil" is supposed always to trump any other form of evaluation, but that is an assumption, probably the result of the long history of the Christianisation and then gradual de-Christianisation of Europe, which one need not make. Evaluation need not mean moral evaluation, but might include assessments of efficiency, ... simplicity, perspicuousness, aesthetic appeal, and so on.

Humans in modern societies are driven by a perhaps desperate hope that they might find some way of mobilizing their theoretical and empirical knowledge and their evaluative systems so as both to locate themselves and their projects in some larger imaginative structure that makes sense to them. ... Furthermore, many modern agents would like it to be the case that the form of orientation which their life has is, if not true, at least compatible with the best available knowledge.

The general point that a political theory is, among other things, a partisan intervention, is well taken. So question about the actual political implication of a theory cannot be excluded as, in principle, irrelevant.

We do not wish to "judge" or assess out surrounding merely as a kind of expressive activity carelessly projected onto the world, but we wish to evaluate the world "correctly," i.e., in according with that it truly is, and the desire to know is directed at determining what the world truly is.