For an organization transitioning its Wi-Fi to WPA2/WPA3 Enterprise with EAP-TLS, X.509 certificates are crucial. EAP-TLS (Extensible Authentication Protocol-Transport Layer Security) is a certificate- based authentication protocol, and for it to work, both the client and server must have valid X.509 certificates. This ensures that the mobile devices can authenticate themselves securely to the wireless network. Other options like IPSec configurations or TOTP tokens are not relevant in the context of EAP-TLS wireless authentication.