Historians of Philosophy

I was wondering today whether it tends to be the case that historians of philosophy hold the view (or a similar position) of the figure(s) they focus on. So, do Kant scholars generally subscribe to some form of Kantianism, Mill scholars to some form of Millianism, etc?

My next question is about the direction of causation. Do scholars usually choose to study to a figure because they agree with their philosophical commitments generally or do they find themselves agreeing as a result of (or maybe just after) having looked closely at the figure's work and found it plausible?

I'm not sure whether anyone will be able to answer this question beyond their own experience, but even that would be interesting to me. This is part of a more general empirical question I have about how strongly people's non-philosophical commitments determine/guide/influence/play no part in the philosophical positions they hold.