What about Frederick's liberal beliefs? He was, if I recall correctly, not on good relations with Bismarck and had plans of weakening the position of the monarch.
They had some sort of a secret rapprochement after the Franco-Prussian War. Frederick wanted Bismarck as chancellor. Bismarck agreed to stay under two conditions.
1. No "English" influence in foreign policy (including his wife, of course).
2. No increase in the power of the Reichstag. (
Dreadnaught, Massie, p. 92).
You have to remember the esteem Bismarck had after unification, and that he did ally himself with some of the "leftist" parties. You also have to remember that he, post 1871, had a peaceful foreign policy. He did his best to defuse situations after that.
Bismarck actually complained in 1874 that he did all the great things already.
It was also Frederick, as Crown Prince, that supported (almost alone) Bismarck in ending the Seven Weeks War, against the opposition of
both Wilhelm I and von Moltke the Elder.
The idea of Bismarck as "warlord in chief" or a more competent version of either Wilhelm II or Hitler needs to be reevaluated.