The referee, Kevin Stott, did not have his best game. The score could have been 1-2 with DC fully-manned and almost half an hour to go. An entirely different match.
But, even if we lived in an alternate universe where Moreno drew the PK and Olsen was not sent off after being mauled, United would have lost. The result was inevitable, and neither tragic nor surprising. It was more like the passing of an elderly relative after a protracted illness and less like the sudden loss of a child in a traffic accident.
Great teams create their own luck. DC has raised its game recently to a level of dreary mediocrity, but this was far from sufficient. Neither great nor lucky (nor well-coached), United went down hard.