Crime's Sesh Tent

In "Moo-ving In", Bumblebee asks Megatron for advice.

Bumblebee: "Hypothetically if your troops weren't listening to you, what would you do?"

Megatron: "When I commanded legions of Decepticons, my strategy was always intimidation. A little brute force. Make a show of my weaponry, that sort of thing."

So even though Megatron is very kind in the rest of Earthspark, it seems Original Flavor Megatron used his physical presence to intimidate his troops and keep them in line. Presumably hanging out with Optimus for fiteen years mellowed him out.

Then there's the fight in "Decoy". Previously in this episode Megatron told Optimus he had reservations about how GHOST was treating the Decepticons. Then Soundwave shows up and Megatron earnestly entreats him to surrender.

In response, Soundwave plays back Megatron's own words:

"This is not freedom."

Megatron roars, "You dare use my own words against me?" As he charges, Optimus reaches out towards him like "Bro, what? No . . ."

By this point in the episode Soundwave had already attacked Megatron and tossed Bumblebee and Optimus around like rag dolls. So you wouldn't think playing one line--which Megatron agrees with!--would be the breaking point, but . . .

You know how an adult can return to their childhood home for the holidays and fall right back into the old dynamics they had with their siblings or parents?

At that moment Megatron fell back into an old pattern: HE was the supreme leader of the Decepticons and one of his troops was being mouthy, which was an affront to his authority. That's my take, anyway.