“Anyone have any idea why this was done?”
Yeah, it’s because a whole bunch of them shouldn’t ever been given a loan to start with, and will likely default.
Reducing the PMI payment, like Obama did, makes the risk even higher. Trump is just acknowledging that there is a good reason why some loans have PMI added on to the payment. It is to reduce the risk to the lender. If the premium is cut, the risk goes up.
This is a good thing. If people want to borrow $300,000 to buy a house and don't have 20% of the sales price for a down payment, they need the PMI to even get the loan. Reducing the premium amount may help the borrower, but it also puts the lender at a higher risk of that borrower defaulting.