The fund will not fall below the principal, but at most it will fall to 0, but in fact almost no fund will fall to 0, because the fund goes bankrupt and is distributed to investors in proportion to its share after bankruptcy liquidation.

If investors don't want to take big risks, they can actually consider money funds. The risk of money fund is relatively small and the income is relatively stable. If you hold it for a long time, you will basically not lose money.