Wikidata already existed during the knowledge engine fiasco, so if it was the same thing im not sure what they were doing.
I suspect a lot of KE's failure related to inconsistent messaging and project scope. I'm pretty sure even now, nobody knows what KE was planned to be or what its value proposition would be, or "what" it actually is beyond buzzwords
The first phase of Wikidata (the MVP so to speak) was purely as a common repository for interwiki links, not a general knowledge engine/knowledge graph. The latter is a lot more recent.
General statements were added in 2013 which is still before KE.
The query service (the SPARQL endpoint) is probably the most KE like part, and that was later, in 2015. Still before KE but much closer. I think (hard to say because nobody gave a straight answer) that KE was more going to be about federation and searching non wikimedia (Free) resources.
