Why do some politicians seems to feel that they are elected to push their own agenda?

We saw so much of that in the Harper-led Conservative Government and now it seems that Minister Freeland s thinks that her personal opinion about disharmony between Russia, Crimea and Ukraine should play a role in her leadership.  It shouldn't.  She's a leader in a Canadian Government and her words should reflect those of the citizens of the country she's part of now.  Most of us trust our government to be a diplomatic one--peacekeeping comes up often.  Ms. Freeland's rants against Russia are not helpful.