Wise or not depends on how the person manages the borrowing money.
Sure, no guarantee of success in crypto. Even I never know if there is an investment that has a guarantee of success.
If the person is a professional trader or an experienced investor, I think it is no problem to borrow money. At least, he knows well how to trade or invest properly in crypto. And he must know the safest way to use that money. And if he can get the profits, just prioritize to pay off debt/loan first. Then, the remaining money from the profits, can be used again to rebuy another coin.