Mature and regulated crypto isn't the only factor that can't make big investors come.
There are big players out there that are still speculating and they are not prepared for the market and they assumes the outcome already. As much as possible they are calculating risk and most of all, they are not well versed and knowledgeable with the market.
There are big players who are already a while in Cryto and might partly be the reason why the bull market has turned into a bear market. The reason are Futures, since this year large financial institutions are able to bet on the price of Bitcoin Futures without risking any of their funds to be stolen or hacked at any of the many still immature exchanges. They simply short Bitcoin and profit when the price goes down. I am in the financial market already more than a decade market and I know my stuff a little bit. George Soros and others who believed in January that Bitcoin is overpriced and went in and bet against it. I have no 100% proof but everything indicates towards it. Do your research and you will come to your own conclusions.
As part of my job I am talking to many clients everyday, some with backround in trading and investment, and I am amazed how few people see this connection.