This is among the most ridiculous statements I have heard about how the markets work. Its actually the exact opposite, the lesser the people the lesser the fluctuations/volatility. And this is not just about the markets, it applies to most things. ex:

1. Single drug company selling the life changing drug = High near-fixed-global price | As soon as more drug companies can sell increase price competition, higher variance in generic pricing, different rates globally

2. All company valuations remain relatively steady until an IPO

3. If a man/woman suddenly gets a lot of suitors their current relationship if less than optimal may crash and burn , in the absence of alternatives the relationship may have a better chance of survival.