Presumably, the "motivation" is that some elements within the human race are essentialy planting 'Thumpers' to attract the Thargoids.
We don't know if the Thargoids are deliberately seeking out these signals and attacking, or they are just responding to those signals in a more instincitive way do we? But either way, the Thargoids have so far only attacked stations where there's a Transmitter. They also then seem to linger in those systems.
The crux of the matter is who/what is placing those transmitters, and why? Unless the Thargoids are inexplicably making human satellites and sneakily placing them, then it's humans that are doing it. So really the motivations of the Thargoids are probably less important than the motivations of whoever is placing/activating the Transmitters?
This also ties into the UA's speaking morse code, the signals they put out (in human lanugages) essentially took us into the Pleiades. In that case it was Alien Transmitters with Human signals. This time it's human Trasmitters with Alien signals. In each case we've been drawn into each-other's territory.
We were shown Meta-Alloys, a materail we can't replicate. Thargoids are being shown Ammonia worlds (or something else, maybe just the singal is enough).
There's always been people (me included) that have said there's signs of human-Thargoid collaborations in these events, right back to the beginning. If we assume that the Oresrian-Klaxian conflict is being played out in-game as it's been suggestd by the novels then the placing of Transmitters to "draw" the Klaxians into attacking humanity and getting us to attack them as they swarm through the Bubble fits exactly into the narrative established in the novels. Since the satellites that broadcast the signals are Human-made, and the stated motivation for the Oresrians was to draw the Klaxians into attacking humanity, then that does heavily suggest a Human-Oresrian collaboration in some significantly deep levels.
The Aegis report on the Guardian-Thargoid conflict indicated that the Thargoids only attacked the Guardians because the Guardians were in the territory established by the Thargoids via the Barnacle-seeding process. As others have pointed out, we aren't in the Thargoid territory. Except, after finding the probes and going to the Pleaides, we were literally directed to the discovery of the Meta-Alloys which started a Gold Rush, and effectively meant that we were well established in the Thargoid territory pretty quickly... There's obvioulsy debate about what they consider territory, but one answer is that it's pretty clear that they established a 150ly-ish bubble around the Pleiades. It's debatable as to whether they would have stuck to that, but regardless, we were all over it, with tens of thousands of ships, dozens of stations, etc.
I think it's interesting that the Federation has always been at the centre of this. Federation ships were the first ones attacked the Pleaides. The first UA's were found in Federation convoys. The "pincer" of the Thargoids seem to be heading for Sol... etc. But I can't believe that the Federation would draw Thargoids to themselves. That would imply that an extrenal faction is manipulating the Feds long-terms to be victims in this drama.
Can't help but wonder if either the suspiciously un-Thargoid-attacked Empire might have had a hand in this. Or the Alliance, who have always had dealings with Alien technology and have long been studying Barnalces in the California Nebula decided that only having the Empire as a rival was preferable.
