Because they believe some of costs they didn’t include shouldn’t have been in the budget and they didn’t leave enough of a buffer with the $4m they left to keep them under. It doesn’t have to be fraud or financial doping, it can just be misinterpretation or disagreement about the rules.
I read one of the issues was spare parts, the FIA changed the rules this year so that unused spare parts are now included in the budget but then applied that to the 2021 budget. I can see why Red Bull would take issue with that.
Sport is going down a really weird path with social media where everyone is a cheat or corrupt, you see it with fans about refs and VAR every week and I’m starting to find it quite boring.
The FIA are useless there’s no doubt about it but this incessant whinging and going way over the top when it’s team you dislike is tedious to say the least.