A Dragon Ball fan has proposed a theory suggesting that the true advantage of Saiyans may lie in their rapid learning and imitation of combat techniques. This ability could also explain why other Saiyans began to master the Super Saiyan form after Goku achieved it for the first time.
In Dragon Ball Z, Goku transforms into a Super Saiyan for the first time out of rage after witnessing his friend Krillin's death at the hands of Frieza. Prior to this event, no one had achieved this form in over 1,000 years, and it existed only as a legend.
Reddit user PrimeLasagna, who proposed this theory, traces its basis back to the early storylines. After witnessing Master Roshi perform the Kamehameha, young Goku quickly mastered the technique himself, whereas Roshi had spent years training to achieve it. Similar displays of rapid learning appeared frequently in early battles.
PrimeLasagna speculates that Saiyans can understand and master combat techniques at a speed far exceeding that of ordinary people after witnessing them firsthand. Following this logic, the difficulty for other Saiyans to transform again may have decreased after they saw Goku's Super Saiyan form.
This theory also attempts to explain how Goten and Trunks were able to master the Super Saiyan transformation at such a young age. However, this viewpoint is derived from fans' observations of plot developments and is not an officially confirmed setting within the series.
The theory also links Goku's learning ability to Sun Wukong from Journey to the West. Akira Toriyama drew inspiration from this mythological character when creating Goku, and Sun Wukong similarly demonstrated the ability to quickly understand and master spells. Whether Toriyama intentionally wrote this trait as a common talent among Saiyans remains unclear.