That's not correct. If you are market cap weighted and Tesla prices crash, that lowers the market cap of Tesla thus making it a smaller percentage of the total

That's not correct. If you are market cap weighted and Tesla prices crash, that lowers the market cap of Tesla thus making it a smaller percentage of the total market cap of the index. Or, if some of the other companies were to take off and increase their market cap, same thing, the fund will need to sell Tesla shares to redistribute the fund by market cap.