First off, to clarify, the event in question was 1901.

Just like his character Sherlock Holmes, Arthur Conan Doyle was always something of an athlete, being fond of a wide variety of sports including boxing, fencing, golf (which he tried and failed to teach to Kipling), bowling, archery, rugby and most centrally cricket, which he kept playing into his 50s.

I have never specialized, and have therefore been a second-rater in all things. I have made up for it by being an all-rounder, and have had, I dare say, as much fun out of sport as many an adept.

He had some concern about his weight in 1898, making a diary entry early in the year with just "16 Stone" (224 pounds, and he was 1.85 meters or 6'1'' tall). Later that same year he embarked on a "course of muscular development" with Eugen Sandow, "The Father of Modern Bodybuilding", and thus was an "acquaintance" of his by 1901. Thus, when Sandow had his 1901 competition for charity (not actually the first bodybuilding competition, despite claims elsewhere*) they knew each other; the other judge was Charles Lawes-Wittewronge, a sculptor (who specialized in muscular forms, The Death of Dirce at the Tate is arguably his most famous work). Both men were of renown at the time in addition to having personal athletic prowess (Lawes was a former college champion in running and rowing).

The charity here was to benefit the British wounded at the Boer War. The judging was set to consider all-round physique; that is, not necessarily the largest muscles, but the most resembling a classical sculpture of perfection. Gold, silver, and bronze statues were the prizes.

Letting Arthur Conan Doyle's autobiography take over:

It proved to be a very big event. The Albert Hall was crowded. There were eighty competitors, each of whom had to stand on a pedestal, arrayed only in a leopard’s skin. Lawes and I put them up ten at a time, chose one here and one there, and so gradually reduced the number until we only had six left. Then it became excessively difficult, for they were all perfectly developed athletes.

A magazine account notes the slow and meticulous process of judging:

Mr. Sandow fairly went on his hands and knees to examine the nether limbs of the men, and not a point seemed to escape the judges, the audience watching with berathless interest.

Returning to the autobiography:

Finally the matter was simplified by three extra prizes, and then we got down to the three winners, but had still to name their order, which was all-important since the value of the three prizes was so very different. The three men were all wonderful specimens, but one was a little clumsy and another a little short, so we gave the valuable gold statue to the middle one, whose name was Murray, and who came from Lancashire.

It ended up being that the winner, Murray, had no money, and Conan Doyle, being worried about him waiting for a train while holding a giant gold statue, offered to get him a cab. They unfortunately were not able to procure one, and they ended up getting a hotel, but not before a surreal early-morning walk through London:

... it seemed to me more grotesque than anything of Steven’s London imaginings, that I should be wandering round at three in the morning in the company of a stranger who bore a great golden statue of a nude figure in his arms.

Conan Doyle did get one more offer of note in a similar vein: he received an offer in 1909 to be a judge for the Jeffries-Johnson boxing match, but he declined.

(*) For instance, 1898 had was a Best Developed Man contest, won by Launceston Elliot, winner of the gold medal in weightlifting at the very first modern Olympics. Interestingly enough, Elliot would not have won the 1901 competition, as his physique was geared for lifting, not all-round balance.

...

Kerr, D. (2013). Conan Doyle: Writing, Profession, and Practice. United Kingdom: OUP Oxford.

Liokaftos, D. (2017). A Genealogy of Male Bodybuilding: From Classical to Freaky. United Kingdom: Taylor & Francis.