Sorry but it doesn't make sense.
Do you mean to say that the stewards were not going to investigate the incident at all, but Ferrari and Alonso, knowing they were likely to receive a penalty for giving Lewis the extra boost, decided to complain about it, with the sole purpose of getting Lewis punished, despite the fact Alonso had finished the race ahead of Lewis anyway?
Or,
The stewards decided to look into the incident themselves, reaching a decision to penalise Alonso, which put him behind Lewis in the race results, but forgot to check all the footage and missed Lewis' weaving, and therefore Ferrari had no option but to draw the stewards' attention to Lewis' weaving, for which he had been reprimanded last year in the same track, hoping this time around it would be more than a reprimand?
I think that the first option is absurd, and the second an absolutely reasonable course of action.
Things in F1 happen in reality as well, not just on video. There were probably a few thousand witnesses to Lewis' weaving on the pit straight even if we did not get to see that on the telly!
PS Imagine an alternate reality where the entire F1 grid was made up of F1technical forum members! Oh, the bitching and the crying!
PS 2. Now imagine an alternate reality where the entire F1technical members list was made up of real F1 drivers. "Yeah, got a penalty, didn't have a huge impact to my shitty race anyway, moving on to the next one!"