> Mortgage interest is deductible and also how would they get fucked by interest in the first place?

Just because mortgage interest is deductible doesn’t mean it it’s a cost that doesn’t matter. There are plenty of limitations on the deduction and it’s not a dollar for dollar reduction in tax liability.

Also, multi-family properties aren’t always financed with fixed rate debt. Those with floating rate debt are already feeling the pinch. And some fixed rate debt has a term as short as 5 or 10 years, which means that a decent percentage of borrowers will be forced to refinance every year at dramatically higher rates than their previous financing.

Some will be forced to default. Projects that penciled out with near zero interest rates could easily be underwater in a higher rate environment.