<p>Considering that Red vs Blue is sub-exists with the Halo universe, an interesting theory would be that Maine is a failed SPARTAN II, for those who don`t know, the SPARTAN II program was known to have some crippling side effects to some of the candidates, such as muscular distrophy or parkinson`s disease. Meta could have been one of these failed SPARTANs and the detriment the program did to him could have been Mental instability, as he is seen as aggressive as sometimes ruthless even BEFORE been the Meta (such as when he tried to kill Texas in a training round).
</p><p>The UNSC could not have just eliminated Maine but at the same time they couldn`t use him the way they would the other SPARTANs or give him some desk work at ONI (As usual with the Failed SPARTANs) so they probably decided to give him to Project Freelancer. Why? Maybe because they would want to see how an AI could further enhance the capabilities of a SPARTAN, this could further be evidenced by the experimental nature of the project and the fact that Maine, at that point would be...expendable.
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</p><p>If you think about it, this could explain some things about him, such as his super strenght or his weight (Average SPARTAN weighs 120 kg, Maine's a big guy, he could have weighted even more) and also his resilience as he gets shot (8 Times), ran over and beaten before getting medical aid. His mental instability could explain how sigma could have been able to manipulate him so easily and he also became proggresively more dependent on him for doing things such as, speaking : Voicing his thoughts and the such.
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