I'm sorry, I just need some clarification. Sentinel made this deal with Megatron way in the past right? Prior to Megatron getting frozen? What was going on in the thousands/hundreds of years between Megatrons crash landing and Sentinels 1960's crash landing on the moon? They were supposed to rendezvous on earth...after Megatron, what, hangs out for a couple of thousand years? When did all those decepticons arrive on the moon to collect the pillars? It would have had to have been post 1960s Sentinels crash, and they just waited for what? Were they waiting for the capability of transporting cybertron to earth? Could they have just flown down and taken over earth during the Fallen's attack in ROTF? For that matter, how does any of this connect to the Allspark/matrix/sun harvester? All of this stuff just coincidentally happens on earth? I'm just trying to figure it out. And just so you know I'm not a hater...I think ROTF actually mostly made sense.
The Ark was nearly destroyed and was floating around in space for a while. There is no telling how long it took them to float through space and crash into the moon. So, in that time, Megatron could of left Cybertron to follow the Allspark to Earth. They make note that in 1963 is when the cons started collecting pillars. The Ark crashed in 1961 and the US didn't land for 8 years. The Matrix and Sun Harvester are part of the same plan. So they were on Earth. Coincidence would involve the Allspark crashing on Earth. And the Ark crashing on our moon...just pure luck.
I really feel like Megatron had two plans. One he made with the Fallen, and the other he made with Sentinel. When he was resurrected, The Fallen was there, so he followed his lead. When the Fallen died, Megatron went with the other plan he had made with Sentinel before he left Cybertron.