:Yes, I took it the same way - that there may have been ruins, or at most :recently ( < 800 years old ) abandoned facilities - perhaps a base of :operations for the Jjaro that warned Earth about its dormant Wrkncacnter in the :1990's.
:I'm sure the Marathon was sent to Tau Ceti by sheer virtue of it being the :nearest solitary G-type star and nearest star with multiple planets, as far as :we know here in 2019.
:Where does the Strauss-Jjaro connection comes from? Is that just your :headcanon, Pforrest, or is there something I've missed?
Sorry, that part wasn't fleshed out well. I guess mostly head-canon, but also based on the fact that Strauss appeared to be one of the leading scientists of his time due to his success with AI, one of the crowning achievements of humankind up to that point.
Not that this is actual evidence but seeing how much Halo takes from Marathon I do think it is worth pointing out that in Halo it is shown that many of the advancements that humans achieve are due to contact with older more advanced civilizations' technologies. Seeing as it is strongly implied that the SO in Marathon is a battleroid and that battleroids were made using found technologies it is not a huge jump to assume that the same is true for the Marathon universe. But as I said that is in no way evidence, just a theory I guess.