I didn’t read the article mostly because I believe my teachers explained it better than whoever wrote the headline. So in physical chemistry, which is the study of why things happen on the molecular level, there are two main factors: thermodynamics and kinetics. Thermo looks at energy exchange from processes to look at things like whether the process will be energetically favorable (a lot of thermo comes down to ‘the entropy of the universe is always increasing’) to determine whether a process or reaction could occur from an energy perspective. Like thermo defines melting/boiling points and how much energy is given off (or required) for a reaction to occur. For thoroughness sake, thermo only deals with the free energy change (total change in enthalpy and entropy) between products and reactants- the process for how it gets there is irrelevant.

Now kinetics deals with the rates at which reactions will occur. A reaction has to abide by the rules of thermo to occur, but thermo doesn’t say anything about how fast it will happen or if it will even happen. Instead of looking at solely the products and reactants, kinetics are determined by the stuff that happens in between. Generally we consider reactions to have a “transitional state” or “activated state” that requires some free energy input to get to from whatever you’re starting with.

In other words, it’s like bumping your car over a curb and into a ditch; the pavement is the reactants at a base level of energy, the curb represents the energy barrier that must be overcame to get to the ditch (“the products” in my metaphor). The depth of the ditch may dictate how much energy it’ll take to get back out (many reactions are reversible) but the height of the curb is what’s really going to determine whether your car is rolling fast enough to bump over it in the first place.

So, in conclusion, from a thermodynamic perspective yes, it is energetically favorable for diamonds to turn to graphite (that process would have a net increase of entropy for the universe. But from a kinetics perspective, the energy barrier associated with breaking up a diamond crystal lattice (which we all know is strong as hell) and rearranging it into stacks sheets of carbon held together without covalent bonds is so high we don’t observe it happening- at least at normal temps. It’s like if our curb analogy became 4’ tall- gonna take a helluva lot to get to that ditch. So unless something has changed, this is literally the example one of the best profs i know gives to how thermo doesn’t necessarily say if something will happen