alt Hacker NewsTailwind was (is?) also selling "lifetime" licenses, which means eventually their sales would collapse anyway, once they have sold a license to most interested customers. They were always going to need to pivot at some point. regardless of traffic to their docs.
To play the devil's advocate, more people are born every day and as long as there are more developers today than there were yesterday, lifetime licenses can bring in a trickle of money each month, especially if the marginal cost of each new customer is zero or near zero.