This is probably an ideal time to learn a bit about ratings and how they can diverge. It's not actually quite so opaque as it is often made out to be.
Broadly, the ratings themselves are about proven
stability. Profitability and growth may be relevant but both are considered from the single perspective of stability. Tesla does not have investment grade because it is
not stable. High growth is an impediment to stability. Rapidly rising margins are impediments to stability.
As investors we value high growth and rapid improvement in margins. We value new manufacturing technologies. Those are distinctly
not stable.
When ratings fail it is either because of fraud (e.g. Enron), large structural changes not obvious from pure financial statements (e.g.Lehman, AIG) or gradual deterioration led to sudden failure (e.g.Penn Central). All of those were visible risks, but all (except Enron, perhaps) were preceded by easily observable problems that were ignored. Bond ratings almost never consider 'subtleties' ('this' because it really means being superficial). On a purely statistical basis, pretty much the rule for rating agencies, disruptive technologies and events are mostly ignored.
High bond ratings thus require, as a general rule, large volumes of ratable securities plus long stability. Disruption is the enemy of stability!
If Tesla achieves investment grade soon (whatever 'soon' might be) it will really be a huge outlier in rating agency practice. It might happen but if it does I, for one, will be astonished. I hope I will soon be astonished. Even with that many Institutional Investors will still be reticent to invest in something so unstable, fast growing and flamboyant.
As investors we have an entirely different and largely incompatible vision.
