Earlier quoted context omitted.
It's hard to say without reading the paper itself, but in general one should be skeptical of claims that such-and-such material is stronger than steel. The properties that make steel interesting are not its elastic modulus or yield strength. This material is probably closer to graphite (which beats steel in elastic modulus and yeild strength) than something you would actually want to use in a structural application.…
I'm curious, in that case what properties do make steel interesting?
But there are a lot of metals that are somewhat stiffer and stronger than steel, like chromium, platinum, and tungsten, while still being somewhat plastic. The great advantage that steel has over them is that it's unbelievably cheap. It's even cheaper than brass, bronze, and lead!
Plasticity (ductility and malleability) is important for a couple of reasons. First, as I mentioned above, it greatly increases the fraction of the material's theoretical strength you can get in practice. Second, it allows you to form the material instead of cutting it to shape. That's the property you're using when you wrap a sandwich in aluminum foil or tie a gate shut with baling wire. You can't do that with porcelain foil or porcelain rod. Third, ductile failure happens gradually rather than suddenly, which is important in some cases.
The other really interesting thing about steel is that it's hardenable. This is very significant because cutting and forming hard things is hard. So it's routine to cut or form steel in its soft state to get more or less the shape you want, harden it, and then grind it and maybe lap it to the precise shape you want. Grinding and especially lapping can be very precise and cut very hard materials, but they're very slow processes.
Finally, steel can withstand much higher temperatures than organic materials, or even most other common metals.
These are, I think, the major reason why steel has so extensively displaced what Andrew Carnegie liked to call "inferior materials".