By all means leave it there — but where EXACTLY is ‘there”. Vanguard has a lot of mutual funds, including money market funds. So you should know exactly which funds you are invested in, and how much risk you are taking. Talk to a Vanguard representative. At this stage of your life, and the market, it is perfectly fine with me if you want to leave most of it in a money market fund! But you should knowingly make that decision.
PS You are not required to take an RMD in 2020.