You can have before and after data and track trends. How did you know the issues was wide spread in the first place. You must have some proof somewhere.

The impact is how many outages overall. If you only prevent one outage then maybe it's not that meaningful.

Your last paragraph, your right that happens in the short term. In the long term those teams get reputations for being a shit show, there will be high turnover, good engineers won't transfer in, people's compentaencies start to get questioned, other teams will avoid working with that team and develop their own solutions, and higher up people will start to look at what's going on.