But retroactively the Queen was at First Contact, and if Picard tried harder to figure out that she existed, he could have negotiated with the Queen, but she wouldn't do that until after he was "in love" with her.
They had bad intel.
Guinin lied.
The Elurians told Starfleet about the Borg, and about the Queen 80 years earlier, but she chose to tell Picard otherwise in Q Who for some reaosn other than what Picard might have told her to say in Times Arrow to complet yet another time loop.