Last time we talked about this the following article came up.
https://fivethirtyeight.com/features/most-managers-are-headed-to-the-hall-of-mediocrity/
However this is about the manager's total effect, like looking at the question 'does the manager make Fred McGriff play better', not just strategy.
The conclusion was the manger is worth a couple games maybe. However that is considering both coaching and managing so to say. So what do Charlie's dumb mistakes alone actually cost? I'm not sure. Would be interested in seeing an analysis, but need something that corrects for player performance. Like isolates the effect of bone headed bunting, from coaching (hitting tips, inspiration, etc.).
Make a chart
Manager strategy WAR (in game decisions like bunting) = X WAR
Manager coaching tips WAR (hitting tips, inspiration, making the guys better, etc.) = Y WAR
What are X and Y if anything?