There are no sides - there are nuanced and diverse issues and varying approaches which optimize for different values and to use words like 'us','them','side' is detrimental to the political process and enables those who yield narrative control over media uncharacteristic influence in a democracy.

Not about sides. Some people are just afraid of things. Afraid everyone is out to steal their kids. Afraid of war. Afraid of immigrants. Afraid of not enough immigrants. This just appeals to those people.

centrists are probably generally less fearful as retreating to one extreme of a polarized dynamic is a common fear response. But I think the point is more, everyone is partially motivated by fear, sometimes governments use that fear as a lever.