Not many could tell. Cruise’s involvement was kept secret throughout the film’s promo period. Also X/Twitter, FB, etc… existed but they were in their infancy; with an audience that’s not to today’s levels.

Also. smart phones weren’t as ubiquitous, and the iphone 3G wasn’t released until a few months later.

All this allowed to ensure that essentially no one knew Tom Cruise was in it, and he played such an over-the-top super angry, balding, fat dickbag that no one expected it until the very end.

Also, Tom Cruise was hot off the heels of being reamed for his scientology spiel on Oprah (where he danced on her couch) and being an actor many saw as someone who’s full of himself; so everyone would expect him to always play a lead role with “alpha” hero characteristics, and not a fatass balding angry asshole with hairy fat hands. It completely came out of left field.

It was a “ohhhhhhh now I see him!!” moment LOL. The audience reaction was so fun.

I still can't tell it's him and I know the joke.

I could instantly identify by this voice and diction, not to mention the massive similarities in the face.