Index funds track an index mechanically. If you run an S&P 500 fund, you have to mirror the S&P 500. If a company gets added to the index, every fund tracking the index must buy it to match the index -- there is no discretion. Pension funds hold a lot of index funds.
So the causal chain is that pension funds track indexes, indexes have to buy the companies in the index, SpaceX got a fast path to the indexes. SpaceX will launch and pension funds will buy the stock, presumably propping up the stock price.
It would take a lot for pension funds to undo this and would be the opposite of index investing.