Why Tribal-class service appears in notable commanders' careers

Why do so many officers in the notable-commanders series have Tribal-class experience?

Because the Royal Navy selected strong officers for the Tribals, cultivated an elite identity around them, and rewarded successful performance.

The pattern partly selects itself. The Royal Navy tried to place its best available officers in the Tribal class, then told them they were serving in elite ships and expected them to behave accordingly. Success in that environment brought further reward, helping Tribal service recur in the careers of later notable commanders.