World wars are government vs government fights, generally speaking. Why do these governments have millions of followers, instead of being ignored like they should when they start wars?

Because of the ideology of nationalism (or patriotism, as it's called in the US and UK).

We've been told we're part of this "team", so if the team wants to go to war, you'd better support it! That's why calling someone "anti-American" is such a tremendous threat socially, because everyone is tripping over each other to see who can support the state the most.

We even have it in our language. We say "The US invaded Afghanistan and Iraq". But in reality, it was not "The US". The land itself did nothing. The people who live in the US generally had nothing to do with the initiation of those wars. It's the government, and the people who support the government even when it's irrational and immoral.

If the government didn't have legions of supporters, there would be no wars, or at least the wars would be much smaller scale.

We're tricked in to thinking identifying ourselves with our nation is our truest identity. People say "I am an American" before they say "I am a Kansan" or "I am a Christian" or whatever identity they have. In modern society, nationalistic identity takes priority. This best serves the existing power structure. It gives them the power to conduct wars and commit crimes in the open. They are above reproach due to nationalism.

This is further compounded by people who submit to the groupthink of a political ideology, be it right or left. They won't scrutinize the wrongdoings of their own team, and they act as though the other teams are causing all the problems. We do this on a scale of nationalism, and on a scale of party politics. And on many other scales too.

Detaching from this web of ideologies is how we unplug from the matrix, how we regain our freedom and stop giving away our power to those who want to control us. People are all too happy to outsource their thinking to an ideology without realizing the full consequences. The less you subscribe to any ideology, the more powerful and aware you are as an individual.