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?
From my perspective, it is financially imprudent (meaning you should not do it) to take out a loan that you are not able to repay absent the performance of your investment (in this case bitcoin). So part of the gamble is that if matters go to shit, you are still able to pay your loan with other proceeds... and that is the cost of your gamble not paying off.
The cost of your gamble paying off is that you end up having more money than you would have otherwise because your investment performed better than the cost of your loan.
The people who lose in these matters are those who are not prepared for either scenario.. and if you are only prepared for UPpity.. then you are inadequately prepared and gambling rather than investing.
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.
You are investing more than you can afford to lose, if you have not already thought ahead about the cost of the loan and your ability to pay it back - either way the BTC price goes. Not a good idea, as you are suggesting, but as you are not suggesting, the mere taking of a loan does not indicate that you are investing more than you can afford to lose, unless you are not financially (and psychologically) prepared to pay for the loan in the event that your investment does not pay off.