Proofpoint

The process was fairly lax with lots of time to do things.

Many. Former CEO ran things poorly and took in managers who brought along their problems and animosities with them.

Not only that, they were allowed to invite their friends to come and join too, many of them owing their jobs to someone creating a bro culture. Even though top mgmt changed since the sale, it's many of these people still there to this day.

Most of the systems were a black box, existing engineers were mostly uncooperative to keep their knowledge to themselves, the offshore engineers in one particular country were especially bad for this. I have seen major accomplishments achieved by someone, where so many others had failed, only to get fired soon after.

I would look to rebuild the operations teams, this was likely the worst run area of the business the former CEO just couldn't understand.

I would also replace HR hatchet women that were only too happy to help these managers bully and fire senior engineers for no fault of their own.