Borrowing money from the bank to invest in crypto is essentially betting on which asset would appreciate more, a currency which suffers from inflation and has unlimited supply or an asset with storing value + utility. So yes, it would be weird not to do it.
If he borrows and invests in a bitcoin and the market is a little dumped for a while, how will he repay his loan? We know the potential of Bitcoin which is a market dump but we don't have much tension. But when someone invests that money by borrowing money and the market suddenly dumps that investor will be under a lot of pressure to repay the loan. So in the case of this type of investment, it is necessary to make money which will not be a big loss even if it is lost.