The ROTJ Palpatine drew an entire fleet to his DS2 by intentionally planting false evidence about its operational capacity for Rebel spies to pick up. He further capitalized on that in his attempt to turn Luke to the dark side by using the situation to make Luke feel desperate. By telling him that his friends would die, he kept manipulating Luke's emotions of fear and anger. And by using his father as Luke's adversary, he ratcheted up those emotions so that Luke would cross the line to the dark. But Palps underestimated Luke (and the Ewoks
).
In the PT, Palpatine overturned an entire Republic by creating a war that wouldn't have existed without his long-term planning and manipulation. He rose to power by playing each side like an ultimate master strategist. And he turned Anakin by identifying Anakin's strongest fear-based vulnerability. Palpatine exploited every weakness in the Republic, within the Jedi Order, and in his new apprentice with precision brilliance and multi-level strategy to gain victory over all of them.
The TROS Palpatine built a fleet of ships that couldn't navigate up!
He built them without being able to have their shields up while in atmosphere, and did so underground so that these shieldless ships would have to break through the ground to take flight.
He announced his presence to the galaxy before his fleet was even out of the ground. His entire plan for Rey was to introduce himself and tell her why he wanted her to kill him.
And then he died because he stupidly refused to simply stop firing his Force lightning, when he could've just used any number of other UNLIMITED POWERS!!
ROTJ and PT Palps: brilliant, but overconfident. TROS Palps: senile and just plain stupid.
It wasn't a matter of being portrayed as overconfident in TROS; it was a matter of being written as an idiot - which is something he never was prior.
In reality, it's more like this: Palpatine corrupts Skywalker (PT), Skywalker avenges and destroys Palpatine (OT), nope - just kidding (ST).