Isn't it ultimately a side effect of a decade of extremely low interest rates, world wide? If bonds were yielding something closer to their historical norms, buying and renting out homes wouldn't be nearly as attractive to institutional funds.
You nailed it. It’s cheap to borrow money and if you have a large deposit you can get a mortgage which your tenants will be paying off. Then you buy another. In Australia you can actually write the interest off as a tax expense. So it lowers your taxable income. With enough maintenance and repairs receipts and a few properties you’ll pay fuck all tax. Awesome way for people with money to make more money.