Who commonly facilitates the PO Sync event?

The PO Sync is an ART event used to gain visibility into the ART’s progress toward meeting its PI objectives and to make any necessary adjustments. The PO Sync is commonly facilitated by the Release Train Engineer (RTE), who is the servant leader and chief Scrum Master for the ART. The RTE helps to coordinate the PO Sync by inviting the Product Owners and Product Management, setting the agenda, managing the timebox, and resolving any impediments or conflicts.

References:

Product Owner (PO) Sync - Scaled Agile Framework

Release Train Engineer and Solution Train Engineer - Scaled Agile Framework

5 Practices to Start Scaling Agile by Mike Hall | Agile Velocity