Not disagreeing that banks make consistent, decent money or that the large corporations want to use the money to pay back banks mortgages.
The point was and is that most of us consider small businesses different than McDonalds. Plus it was too offset what they paid workers. Now large corporations got most of the money and want to use it for paying off capital expenditures. I saw a list of the worth of the corporations and the amount of money they got-all were worth $100M+and got $1M+. (Tried to find the list but it was taken off). Most of them sounded like foreign companies.
Per your point on interest vs principle, if you borrow $100K, 5% interest you owe, $5k in interest first year. Bank charges $791 on a 15 year. $416 per month is interest ($5k/12 months). So you only payed $4500 in principle. At end of year 1, you still owe $95.5k in principle. This is way over simplification.