James Simons is considered one the most successful hedge fund manger of last few decades. He pioneered high frequency trading. Some of the brightest brains work for him.
He has 80 or so PhD in Physics and Maths working for him. They have tested every single imaginable variables.
Before getting in to hedge fund business he was code breaker for CIA
Simons is extremely secretive about his strategies and largely avoids answering questions about it. But Simons was asked in one interview with so much brain power and insight in to market why don't they find long term opportunities.
He said look at it this way , we have tested everything , what we found is if someone says New York as first word of a sentence or thousand page novel. It is easy to predict what next 3 or 4 words he will say after New York but it is very difficult to predict what the next 1000 pages would be about. So it is better to bet on sure outcomes.
That is one way of looking at swing trading. It is easier to predict next 3 bars than to predict next 250 bars. It is easier to predict 8 to 20% move than 100% plus move. Also in sheer number terms there are large 8 to 20% and 3 to 5 days moves.