I don’t see these things as likely to be related. A bad server configuration change or other outage is not the kind of thing for which executives typically are held accountable. If Zuck were going to hold someone accountable (i.e. because the outage tied back to some deeply systemic cultural issue), then the CIO makes more sense as site availability is part of his domain.
The timing of these departures probably is coincidental.
EDIT: I don’t have Facebook’s org chart but I’d be really surprised if two executives for customer-facing products reported up through the CIO or had any touch on infrastructure.
