I don’t understand what Flux hoped to gain in this situation. It seems counterproductive to building a platform for engineers while attacking folks respected by engineers.
They wanted the make sure Adafruit stays silent about the number of active users, and Adafruit gave them some leverage by imo naively reporting a security vulnerability.
What do you mean by "naively"? Reporting a security vulnerability to the vendor is the responsible and ethical thing to do. Suing someone who did you a favor is fucked up behavior and they should be shunned for it.
How many CFAA cases have to be filed in order for people to stop (gratuitously) reporting security vulnerabilities to corporations? Just stop, you don't owe them that, and it always comes off as an attempt at blackmail. If you care so much about their users, report to security authorities instead.
TLDR: Adafruit found out Flux was being dishonest about their user numbers. They also found and responsibly disclosed that they could get their Firebase keys by opening up Chrome's devtools.