So my theory centers around the time traveling, futuristic Kang the Conqueror. Now before I begin I would like to point out that I do no write these often and am only starting to try to write regularly.
So firstly like many others, I believe there is more to the other than meets the eye. In this case I believe that using some technology from the future, based upon Skrull reverse engineering or iron man technology ect, Kang is using holograms and trickery in order to portray the other, whilst the real other has been disposed of. IN this way Kang can manipulate Thanos into seeking the infinity gauntlet and capturing the Earth, which is one of Kangs many obsessions. With the Gauntlet and the Earth in his control he would have ultimate control over all of time. This kind of power alone is a motive in itself.
But what if this planned failed? Surely he wouldn't just rely on Thanos and his army. This is why his manipulation has been present throughout many of the films. Have you never wondered why so many MCU villains have confusing if not ridiculous motives for becoming villainous? Surely Whiplash wouldn't have gone as far as he did just because his father got fired or was screwed. Justin Hammer must have some kind of motive for the hatred of Stark. Many lesser villains from Batroc to abomination to an extent, must have been used in some way to cause the havoc they did. Even Killian must have had better reasoning than being left on a roof top, for hating Tony Stark. This is where Kang comes in. Throughout all their lives all these villains were fed information, brain washed and unknowingly controlled until the right moment to take down Kangs biggest threats. Therefore the force motives in their heads were never very strong, but enough to bring out the hatred in these people. This control slowly neutralized threats and brought the gems together.
So it may be an out there theory but I do believe Kang has been in control the entire time! Why couldn't he just get the gems himself though you ask? Well because he was never on Earth or in Asgard long enough because he had to look after his dying wife, much like the Avengers TV series. His time is collapsing and so he can never interfere directly into what he wants, only through other parties. So that is my overall theory and although there may be some plot holes in this I believe something similar very well may be possible! There are signs here and there for this, from Aldrich Killians space image to the delivery of plans to Whiplash from what we were lead to believe were the 10 rings, but could be Kang in disguise once again.
What are your views on my theory? Ridiculous or possible? Let me know if I left any big clues out also, thanks for reading.