Is it causation or correlation- we play better when more people turn up, but that could be because people are turning up as a result of us playing better? And we complete more passes when we have a bigger croud - that could be because we get worse crouds when it rains and it's harder to complete passes in bad weather.
Yep they really needed to account those things into any analysis. And they could have, it just would've made it all quite complicated - but isn't that what they're getting paid to do? It all Seems really 1 dimensional and obvious (and without context as you suggest) to be worth taking too seriously.