Preseason Performance: Safest Champions Perform Best
This happens almost every preseason. People are way more ham than usual and so safe champions, such as Lux, tend to have way more opportunities than normal. Once ranked starts, people play a bit more of a controlled style and also are more aware of how to adjust to the new season. The aggression becomes more calculated and play-making champions close the gap.
Just be aware of this and don't treat early win rates like gospel. They're often not that reflective of the objective balance state. And no, I don't play Lux (yet). Also, while this is a general trend, I think champions like Anivia do legitimately benefit beyond simply their opportunistic nature. Turret plating lets these types of champions get more benefit than normal.