The number of traders is increasing more than before as more people are generally becoming more interested in ways to become more financially independent and as thus in search of skills like trading.
Does the number of traders directly affect the volatility of the market? If it does, can we assume that trading was easier before with less traders (less volatility) than now when there are more traders, and the market more volatile?
As the market buy/sell demand increases, that certainly affects the volatility of the market price. Less volatility means less activities in the market. That is why we couldn't make ourselves confident of our strategies that worked in the past as someday this is not effective anymore. Traders make the market more volatile. However, we can say it has a negative impact on the market making it too risky, and should look more into market analysis. But on the other, this will also help us active traders to possibly earn more every day.