were they working together or did The Thief just stumble on to the secret of the worm - was The Thief responsible for all of The Sampled?
In conclusion, nobody knows - not even the writer/director. I enjoyed reading all your (very literal) theories anyway.
https://www.youtube.com/watch?v=OI3shBXlqsw
I don't think so but this is just my take on it here...
The parasite has obviously existed in nature before the Thief, Sampler or Orchid Farmers. I think the parasite is possibly unique and indigenous to this part of the world the characters are in, not sure about this part though. What I do think is that the Thief and Sampler are people who have both been affected by the parasite but realized it separately. They figured out the life cycle of the worm (or at least part of it) and found a way to profit from it. Why profit from something so strange and harmful to others? I don't know. Maybe the worm is smarter than we think and has control of how it reproduces itself. However, I think the Orchid Farmers are just unknowing parts of the parasitic life cycle, trying to make a buck on rare orchids.
Instead of thinking about it like the interactions humans have in the normal way. Asking someone to do something and they agree to it for a number of reasons.
Maybe it was more like they had their individual purpose and didn't necessarily need to be in contact in the traditional sense or aware of what each of the stages of the cycle were.
From there you can ask yourself was it an ancient or Alien (or both) parasite that got creatures to do it's bidding.
Or a whole host of other questions. The Sampler, was he the main man in all of this or was he simply infected himself but was serving his purpose in the cycle for these grub things/molecular chemical they produce?
The humans/pigs seem like worker ants or something for this parasitic type creature. All on the same wavelength.
it certainly makes you think, I'll give it that.
I don't know if the Thief he was responsible for all the sampled, I can't say for sure I know for sure what I theorised about above either.
I like the line of thinking that the worm had some sort of control over all those involved, or even were infected by them at some point. Does the effect from the worm ever leave even after it is removed? I think we could accept that it is always there if we wanted to go down that line.
I think they all know of each other, or their parts in the process, however. Could this be form the worm, or are they just those that learned of the process from some other way as if this has been going on for a long time (no way to guess in years really. could be decades, or millennia, or more).
The one thing about them ALL being infected that I don't really subscribe to is the Thief observes the children with the relationship at the beginning as if he isn't controlled by it. Like it's an old family secret. I think he's just part of a long line of those that know, but the kids were infected to be able to produce it properly? Since they were infected they knew, and then once it was done he just made use of it for his own gains.
Then the pig farmer was infected and they all had a connection so he knew of this coming. The people producing the plants I'm not as sure may have been infected, but you don't have to think too much to consider either way.
All in all...the worms were controlling their reproduction cycles by infecting those that they did infect, and it seems they were able to control the minds of those infected to reach their reproductive goals. Of course the Thief at the start was using them all for personal financial gain, which could also be considered as controlled by the worms for the need to have that money to keep the operation going in the first place.