So essentially the Independence Day plot.

"The idea is to create ALIEN terror events and pretend a group of ALIENS are spreading terror."

But that wouldn't be fake, right? They would need real terror events to be believable, especially after mainstream media has lost its credibility. So it's a false flag psy-op.

But, if I were the good guys, what would hinder me to attack the crafts that are carrying out the false flag attacks? People would see UFOs fighting, and that would raise questions, right? And people would want to speak to the ones that are helping humanity, and thank them, right?

Playing that scenario would only make sense if both parties, the terrorists and the helpers, were the bad guys. So, the goal would be to get the approval of the public when the helpers start to take over the governments, like the Companions in the Earth: Final Conflict show. And they wouldn't want to dismantle the death traps.

But how does that scenario serve the bad ETs at all? When the existence of ETs is disclosed and the terror is stopped eventually, people would want to have the technology, and they would want to have the freedom to leave Earth and travel in space, just like the ETs. It would be much harder to maintain Earth as a prison. It would cost much more energy. Why would they do that?

Why would they initiate a fake invasion scenario when there's good guys who will take the opportunity to intervene? And why would they initiate it when there's no good guys who threaten them?

I gave this a little bit more thought, so here's a theory:

They play the problem-reaction-solution game, like I described above. ET terrorists spread terror, ET helpers attack the terrorists, humans will be thankful and ally with the helping ETs. The question is: Why would the bad ETs want to do that?

The only plausible scenario I see is that the bad ETs want to integrate humanity into their empire as a military force. They establish a global fascist government, comparable to the one you see in the movie Starship Troopers. Driven by good old propaganda, humans are then send out to fight "the Bugs" on behalf of the Empire.

"They wanted to increase the population, for slave labour and food etc., so they all hid and pretended there are no aliens so humanity would develop until it's ripe for the harvest."

Well, that would be the Stargate: Atlantis plot, where the so called Wraith were harvesting humans throughout the galaxy. And in that show, the Wraith were smart enough to scatter humans in the galaxy such that they weren't able to develop technology. The Wraith hopped from one planet to another, making the harvest as cost-efficient as possible.

Letting a population develop like humanity on Earth seems to be a dumb strategy. It also seems to be dumb to crash UFOs so humans get even more technology.

If you ask me, there are ETs interfering with the "business" on Earth, such that the bad ETs are cornered and cannot implement their strategy anymore. That could be the reason why they are shipping humans to other planets – they are already preparing for their loss of Earth.