Let me explain: I'm writing a game where the Earth gets a massive biological attack from an alien race in the close future, and only a small part of the planet's life survived (few dozens of humans and animals).
The explanations for those events are discovered by the player during the game, and are:
The alien race is a type III civilization, and eliminates all the intelligent life in the universe that achieves quantum supremacy.
This happens because the only possible way to detect life that is several light years in distance is through quantum disturbance events that are caused by quantum processors, and can be captured by the type III civilization on the other side of the universe instantly.
The biological attack is a viral/bacterial weapon, and the reason why there are a few survivors is because their bodies achieved symbiosis.
The main goal is that the plot is the "solution" to the Fermi paradox. Humans do not find any aliens that are close because all the life in the universe is constantly wiped out by the first race that achieved type III, to protect its monopoly, and they detect a rising intelligent race when it innocently creates quantum computers.
Avoiding plot holes and trying to explain everything to avoid being a "generic alien invasion" is the goal with all that sci-fi, and I think that I can't balance it correctly, because I want to hit a broader audience.
This question relates a lot to my feeling, but the solution does not satisfies me.
My main concern is with the explanation 2. I feel that I need to give the viewer the reason why "only today" the invasion happened and why, and I can't find a better excuse to that. It seems solid, but a bit narrow and forced in my opinion.
I'm open to changing the plot as much as necessary.
Thank you all for the answers. Every one of them contains important tips that I will consider when writing the game.
So, just to summarize:
I will put the deep sci-fi concepts into some optional lore, giving the player the freedom to read if he/she wants to
Focus on the gameplay, fun, battle system;
Avoid over-explanations, as this may cause more plot holes
I will remove the "how" completely. A type III civ is godlike to us and have unimaginable tech, therefore multiple ways to detect life on earth. How they detect is not important.