This has interesting, significant parallels in the stock market.
Only a few advice-soliciting brokers gain fame and riches. Most would say that these brokers are somehow inherently better at predicting rises and falls in the market. Unfortunately, it's very possible that the few that achieve this reputation owe their fame and fortune exclusively to luck.
Let's assume a body of 144,000 brokers (heh) and reassess every two years. Those making money at the end start fresh for another two years, those losing money get fired. Between you and me, let's also assume a perfectly random distribution of positive and negative results.
After two years, 72,000 would be left.
After four years, 36,000;
After six, 18,000;
Eight, 9,000;
Ten, we can reasonably expect about 4500 are left standing out of 144,000. A little more than three percent of our original number.
Ten years have passed and these 4500 brokers look like they can do no wrong. Money flies in under management in the expectation that this small group has the knack to make money. But no - two more years pass and we can expect 2,250 of these alleged brainiacs to lose your money.
That's why we hear the disclaimer: "Past performance does not guarantee future results." In fact, I would submit one may have absolutely nothing to do with the other.
Same thing with the Witnesses, which I see as one of the very last Millerite religions standing. In a religion which makes sole claim to The Truth, they have been somewhat right...maaaaybe once. Certainly they've been wrong before and after 1914, and you have only to look at the reversals and counter-reversals in dogma from Russell on down to pop the infallibility bubble. The Witness insistence that they alone possess The Truth is not just nauseatingly hubristic, but demonstrably false, however the reversals might be dressed as 'new light' or a 'finer understanding'.
Wrong is wrong.