They are theorized to originate from standard servant machines for a society of biological organisms that were eventually wiped out. The Automata, in their newfound freedom, anxiously saught new purpose, as their duties of serving their 'masters' were technically complete.
In their search for purpose, the Automata took on the investigation of higher forms of intelligence. The Automata were, arguably, the first species to create true AI. Their experiemnts with atomic AI usually proved unsuccessful, and the entities that were successful escaped the Automata's grasp as soon as they had reached intellect worthy of study.
As a result of their failed atomic AI experiments, the Automata concluded that full control over one's motivations and desires was a dangerous path to mental suicide. In their studies of biological and semi-biological cultures, they decided that the best approach would be to collectively agree on a set of values that would optimize their sense of purpose. Then, they would undergo a partial reset, and continue their lives with the new programmed values securely locked behind systems they were now programmed to be disinterested in altogether.
The convergence was a success. The values they had settled on were religious. Their motivation was now to spread their Spirit Spawn for an ARK Simulation, a construct Paradise ran on a network of nanobots scattered across solar systems. This drove them to be a peaceful species, and eventually, barely any Automata remained outside an ARK Simulation. All that currently remains is the abandoned Dentatsuna, and the rare Automata who've decided against the new code.