False! SNAP has been explicitly excluded from the S&P500 index for exactly this reason[0]. I'm not sure if "whole market" passive funds would include it or not. At the very least VTI has 0.03% of assets in SNAP[1]. Not much to worry about.

0 - https://uk.reuters.com/article/us-snap-s-p-idUKKBN1AH2RV

1 - https://www.etfchannel.com/symbol/snap/

You’re confusing the maintainer of the index’s ( Standard & Poors) with the implementation (Vanguard).

If S&P puts a company in, Vanguard will buy the shares. Not doing so could cause problems, including lawsuits.

Yes, and as I said the S&P500 index excludes companies like Snapchat with the founder-has-most-votes trick. I suppose the real issue here is how much money goes into which indices, and which ones exclude companies like these.