Unless you’re one of the top dogs in your company, you’ll probably get lost in the shuffle when your company merges with another. This person learned this lesson in the worst way possible when, during their 90-day review, they were told they weren’t a good fit for Greg.
Now, in case you’re wondering who Greg is, the OP was wondering the same thing. They had no idea who Greg was and why they were incompatible with this mythical figure. But none of that mattered. Without even knowing what was going on, they were immediately let go without even a “goodbye and good luck.”