A common scam is to email 10000 people betting picks. To half of them you predict that team A will win and to the other half that instead team B will win. Repeat the process with the ones who got the right picks and after a few iterations you have a small group of gullible people who think you have supernatural sport prediction abilities.
Fund managers do the same thing all the time. They have a portfolio of funds, some of which purely due to chance will not beat their market line and will then be folded into those who did. Then new funds are started to fill the void. This way, almost every fund can appear to beat the market average.
That's just one of the many tricks available to fund managers. Another is choosing the right index to compare your fund against and selecting which time period puts it in the most favorable light. Maybe the performance over the last three years were extra strong or maybe it had a dip so let's compare over the last seven years instead?
The worst thing is that you can't abstain from playing the game. Your retirement money is on the stock market and fund managers will take a big slice of it in fees whether you like it or not.