The index is just a function of the stocks. It only moves if the underlying stocks move. Rebalancing Nasdaq will cause selling in the 100 companies that aren’t SpaceX. And those stocks are held elsewhere too…
The Nasdaq 100 shares 79/100 stocks with the S&P. So if those stocks move (probably down because they’re being sold so SpaceX can get bought) pretty sure that's gonna affect anyone exposed to those companies. Whether that’s directly or through other index ETFs. Many of which have a huge concentration in Mag7 right now, for example.