Yay! People seem to think my theory sucks the least!

Although, for clarification, I had the Lost Fleet of 2328 serving as the trigger that attracted the Shivans, not the collapse of the two Talania nodes. Having a node get so overloaded with ships that it starts barfing them across spacetime is bound to elicit a few 'WTF' moments among those who detected it.
The event in question was first referenced in the campaign 'Awakenings', in which the GTD's Iowa and Moscow appear without warning in the Vasuda system, minus crew, after an unexplained 10-year absence. But despite basing it on something that isn't canon, there is a somewhat canon basis for my theory.
It wasn't until the Gamma Drac Knossos was opened that the Shivans really took notice of the GTVA in FS2. For that matter, the Ancients would have had to have lasted long enough to construct at least the one Knossos portal without construction being interrupted. If the Ancient cutscenes are anything to go by, they had conquered much of the galaxy by that point. As of 2367 the GTVA barely controls 30 systems (and three are in rebellion, too), so I think it's doubtful that Shivans somehow keep an eye on all subspace activity. The Ancients would have been trading and conquering and moving about far more than the comparably puny GTVA.
So that, in my view, tends to disprove the 'Shivans are attracted to normal subspace use' theory. If they were, they would have vaporized the Ancients' empire long before there was any chance to know enough about subspace to build Knossoi.
Ngtm1r's theory is a good one, too, and I think there is a good deal of truth in it (particularly the part about them not being able to tell an NTF ship from a GTVA one until Bosch explained what the heck was going on). But I doubt that they're attracted to
conflict, per se. For all we know, the Lucifer could have happened upon us by chance, or by detecting some sort of massive subspace screw-up (an accident such as the one I mentioned earlier, or possibly a node collapsing earlier than the Shivans had expected, and going to see what the problem was). Or for that matter, the FS1 Shivans could have been lured towards T-V space by GTI operatives as part of the early stages of planning their coup.
We just don't know enough.None of the other theories (MG, Reci, Manifesto) have enough basis in canon IMO:
* MG quite frankly has no canon-ness (which is not to say that it's a bad plotline, quite the opposite

).
* The Nightmares are, of course, not a canon creation, but they would fit the bill of being "part of a bigger problem". I don't think the Reci theory is wrong at all, after all the Shivans did feel they need to have dozens of juggernaughts. But there isn't enough canon evidence for me to openly support it either. That's just me though.
* And the Manifesto... eh. I just can't picture the Shivans being irrationally scared of the GTVA's hypothetical horde of Colossi. Plenty of people have poked other holes in the Manifesto by now, there's no need for me to, really. It's perforated already.
