Why is my mortgage interest being limited?

My primary home was purchased in 2021 with a current loan balance of about 613k.  My second home was purchased in 2010 with a current loan balance of about 262k. Both loans from the two separate properties combined is less than $1M.  Why is my total 1098 interest deduction calculated and capped at $20,640 when I paid much more than that in interest combined?