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ITT: The Chicken or the Egg
Even without smogon, people would still use those Pokemon. Smogon's tiering is based on usage. Those Pokemon are used because they're relatively good, and people's main objective when doing competitive is (Spoiler Alert) winning.
Smogon didn't magically know those Pokemon were great as soon as the game came out. Players found out by themselves.
Really, you're doing the equivalent of blaming the messenger. It's not Smogon's fault that the game is easily overcentralised and unbalanced, it's Gamefreak's.
