I wrote about this at length in Arabic but here are some remarks:
1) I went to the text of the allegiance statement in 1964 when Faisal was crowned. It is interesting that the decision against Saudi was announced "unanimously". No such unanimity was declared in this historic announcement this year.
2) In 1964, Faisal was also declared "Imam of Muslims". They don't say that anymore but Fahd added the title of Servitor of the Two Holy Sites (and the various McDonald's restaurants in the kingdom).
3) Muhammad bin Salman is the first potential king who does not represent a faction within the royal family. He has no alliance to back him up, with his father alive or after his death. Also, the King and his Crown Prince always represented different factions within the royal family: Faisal and Khalid; Khalid and Fahd; Fahd and Abdullah; Abdullah and Salman, etc. There is no such arrangement. By not announcing a Deputy Crown Prince (usually it was said as "the second deputy of the prime minister). The reason that there was no such announcement is because bin Salman has no factional alliances. Worse, Muhammad bin Salman does not even has allies among his own half-brothers. Salman's educated (and relatively able sons) were shunted aside by Muhammad. So don't count his half-brothers as his allies.
4) By disregarding seniority of age and lineage and of generation, Bin Salman established a precedent. This very precedent may be used against him and cause his undoing.
5) The man lacks legitimacy of any kind. Fahd for example, particularly because of his lifestyle, spent lavishly on propagating radical Jihadi Islam around the world, and funding the Jihadi terrorists of Afghanistan (heroes of Western governments). Salman has no legitimacy whatsoever. He has alienated the clerical establishment--many of whom have either been silenced or had their twitter accounts shut down--and does not have credential as a pious Muslim, say like `Abdul-`Aziz bin Fahd (after he came to grips that the Bay Watch actress, Yasmeen Bleeth, was not into him). And his desire to appease the West will lead him to make further concession in the areas of education and religious indoctrination will further alienated the Islamist audience. Remember that most Saudi youth are really close to the Turkey-Qatari alliance than to the policies of this guy. One silly article in some US news site said that among the accomplishments of Bin Salman is the visit by Trump to SA. This hardly will keep his throne stable. His Yemeni war and the current war against Qatar will most likely go down as terrible fiascos. So he has remained the promise of prosperity. How will he reconcile the propensity to please Trump with arms deals with the desire to impose what Western governments call "austerity" measures?
6) Bin Salman will most likely rule but not for "50 years"--as one silly article in Foreign Policy predicated. His style may unseat him--even before he assumes power.
