Unconfirmed report from the Delta crew that the 777 had very minimal exterior lights on during the runway crossing, most likely only the taxi light.
Not sure how it is at your airline - but AA has historically never required all exterior lights to be on when crossing runways. It was never really trained or mandated in our manuals, and until only recently it became a “suggestion” during low visibility and/or night conditions. “Suggestion” - not “requirement.” That has always been shocking to me. Personally as a 737 CA I switch on my lights (landing and runway turnoff) every time when crossing and if the FO does not switch on the strobes/wing illumination I turn those on too. About half of them do it, mainly due to it having been a requirement at their previous airline, not because AA trained them to do it.
Compare this to the Delta flight ops manual which REQUIRES all exterior lights to be on when crossing runways - every time no matter the conditions.
Moral of all this, illuminate your aircraft anytime crossing runways for safety.