Why did it become more profitable to sell them than to hold them?
Yovi, I can tell you never had a mortgage loan.
Elianor is correct, back even a decade or so ago, one went through a microscope over getting aprovval for a mortgage loan. I had to pay off a debt from my first husband that was not even mine, and clearly stated that on our divorce papers, to get mine approved.
Then, banks got greedy, what can I say? I should not even call them banks per se, they were "mortgage lenders." I have no idea what federal or state requirements these places had to answer to. But , after the "dot.com" bust of the late nineties, all of a sudden people were looking for the next "hot market" and it became real estate.
RE on average used to return an overall safe return of around 5%, that did not count mortgage backed securities, which are tied into prevailing standard thirty year fixed interest rate loans.
So, there were two ways to invest in real estate, either buy mortgage backed securities, or invest directly in the speculation that RE prices would go up based on what you paid into it.
Everything went wonko on both fronts about a decade ago, and nobody did anything to reel it in.
Speculation and overinflated prices started cropping up first on the coasts and in Florida and the SW. Then, with the lax oversight on lending practices, lenders started giving out loans to just about anyone, good credit or bad, based on this assumption that the rising value of the property itself could secure the loan, i.e., if one needed to sell, they could do so at a huge profit. These lenders then sold these bundled up high interest only loan packages to greedy investors, who thought they also would make a sure buck.
Do I need to go on further?