I do think the pedestrian overpass would have been necessary: the “status quo” could have led to severe traffic congestion at the Beacon Ave / Pat Bay intersection as turning vehicles waited for pedestrians to cross that wide intersection...
As Mike said, Omicron secured their approvals two years ago, so surely difficulties attracting tenants played a part. Originally Omicron had pitched an electronics/appliance retailer for the centre, so maybe Best Buy pulled out?
That is the wrong place for a shopping center. Maybe a park and ride would work.