Can You Figure Out Why a Simple Circuit Bogs LTspice Down at 700 us

Build : LTspice XVII(X64) (1.7.0.360) Dec 13 2022, 02:47:55 US Pacific

Test case : (Google Drive 8 kB zipped) https://drive.google.com/file/d/1vWl0ZMB6GwsQwaJHG4GdO22Atp_7z30M/view?usp=sharing

This is Robert Erickson's assignment in the Intro to Power Electronics Course on Coursera, from CU Boulder

Won't finish in 20 minutes.. Had to kill it. Why? What did they break?

BTW, Mike Engelhardt's new simulator will be out eventually, hosted by Qorvo.