Case #1: There are two chicken noodle sellers in your area, Rizal and AP. Each shares half of total sales, or market share.
OK, it seems like a fair competition.
Case #2: Still in your area, but now there are five sellers, --Rizal, AP, Aco, Ujang, and Sjamsu. Rizal's market share is 96 percent, each of remaining seller shares 1 percent of total market sales.
Are you gonna sue me for anti-competition behavior based on such market share indication?
Recall: what matters is how many chicken noodle sellers that an addict like
Case #3: Now, Rizal, AP, Aco, Ujang, and Sjamsu decide to set a chicken noodle cartel.
Does the competition vanish? No, they just shift it from the streets in your neighborhood to a table at cafe salemba where they usually meet up.
Case #4: Rizal is spying your house. He wants to steal your BMW.
It's politics. Economics has no answer.