> It was extremely frustrating fighting with people to follow and respect the parent company’s conventions
This post is a tutorial on how not to handle an acquisition! It's generally a bad sign for an acquisition if staff from the parent company say words like that they are "fighting to impose the parent companies culture and conventions"!
It's an acquisition, but companies are made of people, and just because a parent company does something one way doesn't mean that it will fit the company they have acquired.
Take the acquisition of Disney & Pixar. Steve Jobs stated that he wouldn't sign up to the acquisition if it meant that Disney culture would be imposed, because “Disney’s culture [would] destroy Pixar and distraction will kill Pixar's creativity". The whole structure of how the acquisition was planned was to ensure that Pixar maintained creative control and autonomy, and wasn't bulldozed by Disney Corporate.
I've lived through an acquisition too - the real factor to success is to listen and learn from each other, and build a shared way of working. Unless you are buying a failing company, you have to appreciate that they are doing something right and know their own company more than you do. And if it means you use tabs and they use spaces, that's fine.