Mahou Shoujo Ikusei Keikaku as an example of Kraterocracy

Kraterocracy is theoretically rule of the strongest. However, Mahou Shoujo Ikusei Keikaku clearly illustrates than in a battle royale for survival, it not the strongest but in fact weakest that survives and ultimately wins. 

The same will happen if such is repeated IRL. People would simply unite against the most dangerous contenders and eliminate them first. After strong have eliminated each other, the weak and harmless would be left to rule over the rest.

The good examples of that are English War of the Roses, that basically eliminated the entire extended royal family and left the country in the hands of the very distantly related Henry Tudor, who was non-starter at the beginning of War of the Roses.

In USSR after Stalin death, the elite swiftly united against the toughest and most dangerous Lavrentiy Beria and eliminated him first. In the end rather harmless and moderate compared to many of his peers Khruschev took power. Stalin era big names, such as Molotov or war hero Zhukov, were sidelined out of power.

Thus, in reality Kraterocracy leads towards slaughter and rule of the harmless.