My theory is that the shivans don't like us.

This very simple and despicable theory does not explain any of the following questions:
Why the Shivans did not send in reinforcements until 30 years after the Lucifer's death.
Why the Shivans OMGWTFBBQSALAD'd up Capella.
Why the Shivans in FS1 did not have beams while the ones in FS2 did (among other differences).
What the Shivan Comm Nodes were.
How the Shivans got such a big fleet.
Why the Shivans only attacked subspace nodes, except for Earth, Deneb and Vasuda.
How the Shivans are the "Great Preservers".
The Origins of the Shivans
However,
MY THEORY answers all these questions, AND MORE, including, but not limited to:
Why some nodes which appeared in FS1 didn't appear in FS2.
Why there were more than 1 node to Sol but all were destroyed by the Lucifer.
Why the Shivans have flak!
Explains Petrarch's "Shivans are exiles" comment.
Read it and be enlightened.