It's not like there are no risks attached to a Bitcoin investment but it depends on the type of the investment, the time, and market conditions. When you invest in Bitcoin by buying some bitcoin from the spot market when the price is pretty low, you tend to have a very low risk of losing money because the market will probably go up from that point and then you can sell your bitcoins and earn some profit from your investment. However, if the same investment is done when the price is high and then it goes down, if you are patient, the risk is still low, but if you are new and impatient, there are risks that you might sell your assets and incur a loss because you bought them higher and sold them lower.
Other than that, futures and other trading markets carry substantial risks.
In addition to the risks that bitcoin's volatility brings to us, there are also security-related risks such as hackers, and loss of private keys...all of which will cause our bitcoins to disappear without there's a way to get them back.
Furthermore, the legitimacy of bitcoin is also a risk that we should not ignore. Although bitcoin ETFs have been accepted, there are still many countries that have not legalized or even banned it completely.
Honestly, I have not seen any asset that can give high returns with no or low risk, including bitcoin. Those who say bitcoin is risk-free are just trying to exaggerate it more than necessary.