What if the humans found an almost dead Starscream and offered to save him if he were to share cybertronian tech with them. Only to find that Starscream had his own agenda of reviving Megatron/Galvatron and contacting Lockdown to destroy everyone else?.
That sounds more like something Bayformer Soundwave with his human network would have done. But yeah, giving Starscream a behind-the-scenes plan should have occurred in the films.
Would prefer if it wasn't Starscream who resurrected Megatron/Galvatron - simply because it would be Starscream simply obeying Megatron/Galvatron. Would rather have Megatron/Galvatron resurrect Starscream as Cyclonus then have Starscream/Cyclonus betray him. Also the theory seems a bit of a waste for Lockdown - as they are kind of hyping who sent him and I feel anything less than either aliens (Quintessons) or the god/devil (Unicron) would be a massive disappointment.