There are plenty of reasons why Medium is losing writers to Substack. The number one is money. Substack pays directly to the writer when one is a paid subscriber. I just opened my substack and have eight paid subs. Granted, I'm not Heather Cox Richardson and never will be, but I need to supplement my income and save money for travel and future expenses. When I migrated over here from wordpress in 2016, no one got paid except very few. Then they opened it up and people started getting paid. Around 2020-21, the payments for top writers like Christine Stevens, Jessica Wildfire and Shannon Ashley went poof. I have roughly 700 followers on here. I'm not sure if I'll ever get to the level of those three, but my fate was sealed a long time ago.