I don't own Invader Zim.
Zim didn't want that to happen to him, he didn't want to end up like those scientists. He wanted to be remembered.
So he tried his best to make an impression. He tried his hardest to be noticed, for everyone to know his name.
He knew that success of a short irken would not be paid attention to, that was the way irken society worked. The attention span of the masses are very short, and when the leaders try to lead the attention away from such achievements for their own gain, it works. No, the only way for Zim to be noticed was to act like a complete idiot. He was called a defect by others. If not being ignorant meant that you were defective, then Zim was very happy to be such.
He yelled, spoke in third person, and constantly craved for attention. The icing on the cake was Operation Impending Doom, he tried his hardest to fail, and fail he did. Zim ended up getting banished for his efforts, but he knew that it wasn't enough. He had to work harder, so he "quit" being banished and made it to Operation Impending Doom II.
Zim knew that the mission was a fake, he knew that he was being ridiculed by his people, but he was noticed and remembered.
The earthling boy though, that was something different. He wasn't just noticed, he was the subject of someone's obsession. The game they played together was dangerous, and Zim even had to get serious sometimes. He didn't want it to end. He made his plans easy enough to defeat, but was always smart enough to avoid his own demise.
His people knew him as the worthless invader, the boy recognized him as a constant threat. He had fulfilled his life objective, he wouldn't be forgotten anytime soon.