Apparently, there was a conspiracy type theory quote said to belong to Marx circulating, which mentioned the deliberate policy of getting the masses into debt, but experts can find nothing to indicate that Marx said it.
I'm not sure if Marx said it, and it's not a conspiracy as such, but the reason people get in to debt is because of the contradiction of Capitalist mode of production:
The Capitalist wants the difference between the amount paid to workers for their labour, and the cost of the product sold back to workers to be maximised. Put more simply: business will obviously try to push down labour costs, but sell their products at the highest price possible.
The contradiction here is that in order to the business to stay in business, it needs to sell its products. The problem is, if workers don't earn enough money to buy the very products they make themselves, which are then taken away from them, and then sold back to them, then Capitalists can't make any profit.
I noted on another thread I just started that this is partially what caused the most recent economic bubble. Wages have been stagnating or falling for the vast majority of people who work for about three decades now. In order to keep the machinery going, they have to make cheap and easy credit available to the masses, so that they could keep on consuming.
That's why credit was so easily available, and dodgy credit was re-packaged and re-sold so as to hide risks. Credit agencies were actual private profit making companies themselves, so they were hired on the basis of giving good ratings to dodgy credit.
So bad credit was bought. Credit agencies rated the debt as good, since they had a strong incentive to do so, and so the debt was then sold on as 'good' debt.
Eventually, there was so much bad debt in the system, but nobody knew what was good debt or bad debt, and the whole house of cards collapsed.