Civil servants are a-political so why would you need to fire them? A civil servant carries out whatever law is enacted by the government.
The bureaucracy is a tool and tools don't have a will.
Have you watched the British documentary series "Yes, Minister"?
As if it's not made of humans. This view is in grave error. Nobody is perfectly rational, nobody is beyond bias or subjectivty, nobody is beyond human emotions.
Building upon economic theory, public choice has a few core tenets. One is that no decision is made by an aggregate whole. Rather, decisions are made by combined individual choices. A second is the use of markets in the political system. A third is the self-interested nature of everyone in a political system.
For certain classes of politician, this might actually be a problem.
Civil servants are people like you and me, and have as strong will as anyone.