I wouldn't call the modders stupid, whitespace and mixed-case letters are perfectly valid for folder names after all. It only becomes a problem because Content Manager is inconsistent in handling folder names (=carId) for read/write operations from/to their internal storage. Some write operations seem to lower-case the carId first, some don't. Same goes for read operations.
Here's an example:
Take a car with no recorded stats and uppercase some of the folder name's letters, then drive some laps with the car.
Content Manager will display the best lap but no mileage on the car's detail page.
View attachment 1143771
Now Quit CM and change the folder name to all lower case letters, then open CM again. The best lap is now gone but the mileage is displayed (it might be necessary to press "Reload" once to update the stats in some cases). Edit: turns out quitting is not even required for CM to pick up the changes.
View attachment 1143772
In any case this should be an easy fix in the CM codebase and nobody would have to talk about this ever again or go through their 3k mods to rename their folders or write a powershell script or whatever.