A long, long time before humans knew of their existence, The First were observing them, and they were worried. Humanity had just started developing primitive yet highly destructive technology of planet-destroying capability. They had to be watched, and kept in check if necessary. If you look closely, at just the right angle, you will see the threat...
In this particular case, The First did not need to interfere directly. They encountered what the humans called the Death Star just as it had been completed. A full structural analysis revealed a clear weakness that almost seemed like a deliberate design flaw. Probability estimates were high that it would be destroyed by the opposing human faction before it could do too much damage.
Even so, The First decided to watch humanity from afar, just in case. Eventually, after the humans developed their Neuralnet and became a peaceful species, it was no longer necessary.