Latin root fus means pour
Comes from Latin fundere which means pour, melt, inject, fill, irrigate, gush, etc. The first idea is the object is about is liquid stuff, it can be water or metals in liquid state. The second idea is the action of fus is unthoughtful(kind like no brainer), without careful scrutiny and check, unpurposeful, when you use it to describe the huge amount of something, you mean there is quantity but no quality, the more doesn't mean better, it's usually negative. Say you got a profusion of information, it means there are a lot of information but most of them are just garbage and junk like many things on internet, the sheer quantity doesn't mean there are really useful for you, that's why we need Google and Facebook recommendations, without it we will get lost in ocean of information.
- A Russian security think tank, says the profusion of armed robots is slow, as many get no further than the proposal stage.
In this sentence the profusion means the speed to adopt armed robots to proliferate it is slow. It should be slow, armed robots are autonomous killing machine, it has some serious ethic controversies, the profusion of it is doubtful and should be considered carefully.
Let's see the word confusion, con means together, like mentioned above, gather a lot of things together without careful check and critical thinking, the only result is confusion. Human brain is not good at processing a lot of things at the same time, that's not how human brain works, it must learn things step by step, each time with a small piece of it and gradually you learn stuff.