From what I know, it's a combination of prerequisites (can you manufacture this? can you conceive of it?) and pressures (what problems are most people facing?).
There's also maybe some selection bias; most (all?) of us hadn't heard of the other two cubes, because they failed to catch on for various reasons; if a cube had been invented sooner, would we have ever heard of it?
There's also maybe some selection bias; most (all?) of us hadn't heard of the other two cubes, because they failed to catch on for various reasons; if a cube had been invented sooner, would we have ever heard of it?