The dead person can't make bad decisions on when to buy/sell the index fund. Those "bad" decisions don't even require an attempt to time the market, if e.g. you always invest whatever's left over after ~fixed living expenses, and you get paid more when the market's higher.

Index funds have a deterministic algorithm to balance the portfolio. Hedge funds can predict this and always be slightly ahead. So whenever an index fund's algorithm says to buy more of something, a hedge fund probably bought it a fraction of a second ago and will now sell it to the index fund at a slightly higher price.

At least, version 1 of hedge funds did this to version 1 of index funds. It's now so complicated that all you can count on is the smartest, fastest-moving guys having a slight edge.

Even index funds have management fees. They're very low now, to the point of not mattering a lot, but it would still explain the ranking.

There's some other interesting effects with index funds too. Sometimes the price of ETF index funds gets out of whack with the actual holdings. When that happens, there are corrections that get brokered with well bank-rolled partners. This probably accounts for a bit of performance loss as well.