This same exact thing happened with my startup. I was surprisingly the second engineer to trickle out, which is only surprising since I didn’t expect someone to leave before me. The clash of cultures made it difficult to integrate; different geographies, age brackets, experience, practices, tech stacks, you name it.

Overall, I agree with the theories proposed in response to your post — either incompetence of their leadership or favor to an investor. In our case, it was a bit of both and the latter part was clear beforehand. Their crudely constructed plan was to take our industry data to improve their models, but they were not privy to any of it so effectively all they bought was a bunch of tech they couldn’t manage to integrate since all of our tech leads left in the first two months. That’s what they get for not providing an incentive to stay at all, which again hints at both incompetence and a favor.