Regulation.
Stay with me, I will explain. Regulation will need more investors, the more investors can buy bitcoin .
You mean regulation makes btc attractive ? To some yes but for most no because they prefer bitcoin the way it was meant to be .
If there is more investors, there are money in market, the more money in market - less volatility.
I dont think that more money will result to being less volatility . more money means the value of btc will pump , most people will only sees that as a good opurtunity to sell so the value will drop rapidly ,the decrease of the price will also be an opportunity for the people to buy. see ? The value is still up and down . not stable