The First Transformers was about the All Spark and how it can create and destroy worlds and whatnot Megatron wanted that so he can fix Cybertron. Earth happened to be cUght in the middle because that's where the all spark landed.

Two is a continuation of the first but Megatrons team is in shambles as he resurects an old Prime to do his bidding, but is quickly tossed aside by this new ancient prime for being more prime.

Three was as close as Megatron will get ENSLAVING our race and bringing Cybertron here.

As you can see it wasn't about World Destruction, but Domination the entire time. Watch better please, I also didn't like these movies much because Shia