Congratulations for walking this line correctly.
I agree that some sort of market validation is necessary to at least pretend you are on the former not the latter. Those early usage spikes are helpful reminders that there is a business here somewhere.
I'll also make a note that you spent time on marketing from the early days. Writing blog posts, promoting said posts, having a Discord server, committing to answer emails, all of this is marketing and its likely lead to success more than the code.
I notice whenever there was a dip in revenue, marketing (in the form of more blog posts) was the response. I suspect that was intentional, and definitely a better approach than "let me go away and silently code more features."
So there are valuable lessons to others here. Congratulations not just on the current success but also on sharing the path that leads to success. Ultimately you can show the way, but you can't make people learn from it.
Oh, and I like the bootstrapping approach. I did the same, and I'm not sorry. It's longer and harder but also skips an enormous amount of extra work.