Same can be said about every company, acquired or not
It’s a fundamental change in dynamic.
Leadership, however, has changed.
(Extreme example, there are many others. Carly Fiorina's demolition of HP comes to mind.)
The CEO of a different company in charge isn't that different than an internally sourced CEO in charge.
If you want to boost numbers this quarter and don't care too much about intangibles, the incentives really push towards gutting the acquisition.
A CEO of an independent company has different incentives to a CEO of an acquirer.
The culture of Microsoft has gone through radical changes between gates, balmer and nadella.
But a culture isn't _only_ a reflection of the leadership, it's all the interconnections of people and organizations within the whole company.
A leader can come in and make changes, and often these changes first have to break everything that's there already; without care what replaces the broken structures is just chaos; by default that chaos is the governing culture without more inputs and work from leadership.
These changes are most pronounced when 2 large organizations become one because both cultures have inertia (whole foods / amazon, slack / salesforce, etc). But yes, of course when CEOs change there's change to the corporate culture, but because there's only the force from the CEO's changes not entire cultures bashing into entire other cultures, the changes tend to be more gradual.
I am not an MBA or sociologist or really anyone with a worthwhile opinion, I've just been around the block and have the stories to tell or retell...