If investments didn't grow at a faster rate than interest, why would anyone ever invest money at all instead of putting into a savings account? I don't know why it''s hard to imagine that a large loan with a relatively low interest rate might be able to be invested for more than enough profits to pay off the taxes and the loan with some to spare
I'm not a tax lawyer, but I think if you default on a loan, the collateral changes hands, which is a taxable event for you as if you sold the asset, at whatever value the unpaid portion of the loan was. So you pay tax.