So let me tell you why the 'simple' model failed

1. A simple model can me simply exploited by simple humans and simple bots created by simple human. So those simple humans started to simply grab the reward pool for their personal gains, because it was simple to do so without any guardrails in place.
2. If you have an exploit in this space, simple people will always misuse that exploit because its simply easy to do so.

In order to prevent those exploits, we had to add complexity to the game so that the simple exploits can be prevented. So either you change simple humans or change the simplicity of the game. We couldn't do the first, so we did the second.