As I learned long ago, don't expect venture-backed and post-IPO startups to act "logically". It's all a big hustle and a scramble for market share and whatever other metrics. There's a lot of collateral damage along the way, employees and customers be damned.
Startups aren't a "meritocracy" and management teams don't operate by best ideas win. Markets are brutal, management teams are opportunistic and often self-serving, investors are focused on growth at all costs and hitting metrics, and companies don't operate in ways that suit logic. They suit the needs to capture markets or do whatever they do to get ahead. Sometimes ethically, sometimes not.
C: The calculation that caused this was probably some black-box political battle that was won by Manager A, and lost by Manager B. It was probably decided based on personal preferences and biases of decisionmakers, as well as on who was friends with whom. Decisionmakers that run private corporations make these kinds of decisions all the time, and any attempts at reading the tea leaves, or the chicken entrails, to try to predict or explain these decisions is likely a waste of your time. If you'd like these decisions to be made in the open, you need democracy and transparency, which is not something that's is selected for in the modern business world. This is not a value judgement of the modern business world, it is just a descriptive statement about it.