Optimization has a role but it's more than that.

Exynos has better benchmarks because those test peak performance, you only get that performance for a minute before the GPU/CPU throttles to prevent overheating. Only andandtech tests this, because they have the technical knowledge to know this unlike YouTubers which just look at peak numbers and think that's how their phone runs 100% of the time.

Unless you're running an app for just a minute, the Snapdragon completely destroys the exynos in terms of battery life, running apps, and of course it has far superior developer support. Optimization plays a role, but the chip is also better in terms of running apps for a longer time and more efficiently.