He's been on his way out for quite awhile, having stepped back from day to day operations in July '17. He wasn't the most professional leader and was widely blamed for promoting and perpetuating a toxic culture within Moz. This included publicly attacking people in the industry, openly mocking and punishing customers for criticizing his product(s), and politicizing honest feedback. In addition, blew a ton of money on pie in the sky ideas that led nowhere while letting the core product stagnate, only having to lay off 30% of their workforce.
Never worked there, take this with a grain of salt, just the word on the street in startup land :)
Never worked there, take this with a grain of salt, just the word on the street in startup land :)