If an industry is overweight PE, you can bet that the market analysis looks fantastically attractive (competition isn't too fierce, suppliers have little power, buyers have little power, not many substitutes, and little perceived threat from new entrants). If a clever entrepreneur can render that last condition false and enter that market, that entrepreneur has the opportunity to shrink and consolidate a $huge market that's owned by PE players into a $smaller market that is owned by the entrepreneur.
PE controlled competitors will, generally, not be particularly agile, because PE tends to capture value by leveraging the heck out of a currently viable business model. It's a model that works really well as long as base assumptions hold true, but startups can ruin that for them.