While Crowley's family was fairly well to do, much of their fortune was based upon the family brewery, Crowley's Alton Alehouses. While this business was quite profitable, it was also the type of industry that was still looked down upon by the traditional British aristocracy during this era. Even the Great Beast himself seemed somewhat embarrassed by the source of his family fortune. What then would a man like Lord Salisbury make of a brewer's second cousin? Likely he would have been perceived as petty bourgeoisie, at best.
But keep in mind that the Cecil family maintained its historic power by recruiting men of ability into its ranks. Crowley was already an accomplished mountain climbers by this point and undeniably brilliant. This may well have made someone take notice.
Another potential clue is provided by the career Crowley had hoped to use Cambridge as a stepping stone for: namely, in the diplomatic service. Incidentally, this type of work has often gone hand in glove with spy craft as well. Indeed, diplomatic cover is a time honored tradition among spooks. And that is why Crowley's involvement in the Society for Psychical Research at Cambridge is so curious. Consider one of the individuals he encountered in the SPR at Cambridge:
"Another man who enjoyed intrigue was the Hon. Francis Henry Everard Joseph Feilding (1867-1936). Finding Catholicism inadequate to cope with grief at his sister's death, Feilding joined the Society for Psychical Research (SPR) in 1895. Established at Trinity in 1882, the SPR investigated scientifically 'psychical' phenomena: mediumship, telepathy, ghosts and life after death. Feilding, SPR secretary from 1903, was also an intelligence officer. If anyone recruited Crowley for secret service at Cambridge or elsewhere, or at a later date, Everard Feilding, Crowley's senior by eight years, must be a prime candidate.
"A 15-year-old midshipman in the Royal Navy during the Egyptian campaign of 1882, Feilding was admitted to Trinity in 1887. Called to the Bar in 1894, he served on the Committee of Naval Censors (Press Bureau) during the Great War, and afterward, with the rank of Lieutenant RNVR, in the Special Intelligence Department of Egypt. In a career move similar to that which launched the legend of Lawrence of Arabia, Feilding was lent to the Arab Bureau and the Foreign Office for political service in Syria. After the war, he received the OBE, as well as the Order of the Nile and Order of El Nahda for services in Egypt and the Hejaz. Feilding was Crowley's intelligence contact when, during the Great War, the Beast spied on the German propaganda machine in New York."
(Aleister Crowley: The Biography, Tobias Churton, pg. 33)