The original idea was that the humans were used as a kind of biological processors. Like a botnet but with humans. That idea is so much better, but studio execs shot it down because "people wouldn't understand".

I don't know why but for some reason the Thanos one bugs me more, it feels more fundamentally wrong. Like I understand the flaws with the matrix, I went electrical engineering to software development, but to me I'm still willing to accept some wand wavy bullshit about how they need to harvest humans for power, more than I am that a population won't double immediately. Like the biology of consciousness and brains and electricity have a lot more room for complex weirdness than the weeds in my walkway always immediately regrowing.

The original script of The Matrix didn't day that. The original purpose was to use human minds as computers to fight other humans. Butt if you think about it, Morpheus though he was living in the real world.