I agree that its a bad decision but I can see the attractiveness with the market as it has been for the last year.

Also interest rates are at an extremely attractive low rate (at least they are in the UK).

So lets say you borrowed around £7000  6 months ago and bought 1BTC.
That BTC is now worth around £26000 -
Sell now and pay off the loan and interest (around £250) and you've still made nearly £19000 profit.

For some people they will look at that and say getting a loan is worth the risk. The mistake of course is over-optimism that the price will keep going up in the next 6 months in the way it has for the last 6 months.