I don't understand why it's crazy to take a loan to buy bitcoins, it's only crazy if you have unrealistic expectations of bitcoins value going up. The nature of bitcoin is that its value can only go up, because of its fixed supply and harder to come by as time goes. The nature of fiat is that its value will go down, because of its unlimited supply and inflation. Simply put, if you buy $1000 worth of bitcoins now, that $1000 bitcoins are gonna worth more than $1000 in the future where as the same $1000 worth of fiat money now is gonna worth less in the future.
Your statement is logical if your premises are true. But I don't think they are. Bitcoin value is not a one way street. It can and does drop in value. And it may stay down for a year or more. It is still in beta and a true fatal flaw could be discovered anytime. Bitcoin should still be considered a very risky thing to invest in. It was never designed to be an investment and does not behave like one. The only thing that is sure about the deal the OP has contracted for is that he now owes the bank the money he borrowed AND the interest AND the late fees if he runs into a cash flow problem. The bank is going to make a profit no matter what. They are the smart money here.
Bottom line is that the op now owns far less than he borrowed. In order to make payments he must be selling the coins he bought for a fraction of what he paid. When he is out of coins he may be in serious debt. Next comes his stuff, his car, his house.
The way to have done this is to buy tiny amounts you can afford to lose over a long time horizon. If he had done that he would have less coins, but he would have gotten them at a better price. Most importantly is that he would have coins, not debt.
