Aside from the deliberate misdirection in trailers, the Russos also made sure that the cast and crew involved in the movie are tightlipped about Infinity War.
In an interview with Variety, Joe talked about how he and his brother pulled off in balancing what narrative to follow in Infinity War.
Joe and Anthony Russo reveal that they deliberately used misdirection in Avengers: Infinity War marketing, particularly in the trailers to make sure that fans can crack the film’s overall narrative prematurely.
And with Infinity War their biggest undertaking yet, the Russos couldn’t risk even the slightest possibility that people found out about the movie before it even rolled out in theaters.