I'm in the midst of a similar situation to the Slack team, but on a smaller scale. Our app is a product of the people and the culture. You can't just steamroll the culture and not affect development and the end product.

I've been really surprised at how naive senior people in our parent company are on this front. Many have spent their whole careers at this one company, so they have very limited understanding of anything that doesn't align to what their company does.

Combine this lack of experience with a big dollop of hubris (they work for BigCo!) and it's easy to imagine a well-intentioned executive destroying the value of the acquired team and product.