The market develops in cycles

There are many theories on how many cycles there are, how long they are, what markets do well in what cycles, how to recognize what cycle we are in, ... 

One thing is not debated though: There are market cycles, and at different times different types of companies do better than others. Of course, on top of this is also the fact that there is always new companies established on the market that finds a niche that works fine for them and do good for a long time independent of the current market cycle.

No single company will beat the index independent of time and market cycle, so in order to beat the market long term, you will need to switch what markets and companies you trade.