As initially reported by JonNYC and appears to be confirmed on CAPA, PHL-MEX is gone in January. So they gave this route 4 months before announcing the suspension, 2 of which during the slower Fall shoulder season. There was quite a bit of optimism around this route and while I do not have numbers I thought there was a reasonable PHL-MEX PDEW that could support the flight.
American Airlines to suspend Philadelphia-Mexico City service