IOW, he viewed his action as akin to taking a new name, one that doesn't belong to anybody else, so he doesn't think he is stepping on somebody elses toes (beyond those he is deceiving with false ID).
The facts may speak otherwise to this. If he knew there was some sort of history associated with this "new" ID, then that history has to belong to somebody else. SCOTUS is adept at ignoring facts, and at ignoring law.
And why exactly are the claims of an illegal alien believed? His claims as to his state of mind? Illegal aliens will lie through their teeth because living here is very precious. Which most Americans are oblivious to
Offhand I would say living here as an illegal alien is worth $300,000 over a 20 year period. It is worth more if you are a legal resident (green card) and much more if you are a citizen because then you can import in (legal immigration) your raggedy-arse, ill-educated, illiterate 3rd world family members.