Did I say Enma was not a factor?
I have said that I don't think Zoro could have pulled off such a powerful Hiryuu Kaen with Wado Ichimonji.
Zoro has used Enma twice already this battle:
- His Rengoku Oni Giri that struck Kaido
- Deflecting Kaido's Destructive Wind
Neither Big Mom nor Kaido noticed the blade then, but when Zoro overflows his haki through it in preparation for an attack, they notice Enma.
The simplest explanation was that it was the power being coursed through Enma that alerted Big Mom. Supporting this is Mama chastising Kaido for greatly underestimating Zoro after he launches the attack: