This is why momentum investing works. And it is self reinforcing. From Tom Brakke:
Machines ~ While there are quantitative strategies of all kinds, many are driven by what’s worked and what’s working. The absolute price levels of the market or of a security are of little concern; it is their movements that matter. And, yes, the machines might even trigger actions themselves with some “momentum ignition” if that has proven to be successful in the past.
Momentum players ~ Wherever the spark of momentum comes from, there are large numbers of momentum traders/investors in the market. As confirmed by academic analyses and supported by sociological observations, price momentum is a powerful force and it drives behavior by lay and professional players alike. Some forthrightly state momentum as their strategy, while others practice it under cover of a more marketable philosophy.