Investing in Bitcoin is not risk free especially to investors who do not invest appropriately with the right approach and strategy, and also not sticking to their investment plans (long-term).
I disagree with your statement partly because long term investing is not risk free. Investing in Bitcoin or other coins certainly involves risk. If you are a professional investor then you are used to taking risks as the price of any currency is not always the same and fluctuates constantly. This is the picture we see in the cryptocurrency market.
However, although the investment involves risk, the level of risk in Bitcoin investment is relatively low. The risk level of Bitcoin investment is low because investors buy and hold the currency for a long period of time by buying and accumulating small amounts in what we call the Dollar Cost Averaging method. If you want to earn substantial profits, investing in this method requires you to plan to hold the investment for a long period of time.
Long term investment is the best investment when it comes to bitcoin investment because it is the only way you can get it right, when you are involved in short term investment it will make you turn to a trading which will likely make you lose money or get little profit so is better to be patient and keep accumulating using the DCA strategy.