Okay, here's why I think the movie wasn't popular (mind you, I liked it, but I'm aware a lot of people didn't):

1) It was incomprehensible if you weren't a fan of the show. Most movies based on tv shows try to do a compromise to make them accessible to a new audience (see, for example, Joss' opening sequence for Serenity, which was clearly there for people who never watched a single episode, though he tried to make it fun for old watchers as well), and Lynch didn't. So when this film was shown in Cannes, as opposed to previous Lynch efforts, the effect was much bewilderment.

2) If, on the other hand, you were a fan of the show, you probably wanted some follow up on the big cliffhanger - Cooper possessed by BOB - , not a prequel. While there is some follow up on the cliffhanger via Laura's dream of Annie, which gives us at least a hint of what might happen, this is determinedly a prequel, not a sequel.

3) The film has a prelude with characters the fannish audience doesn't know (like a satyr play before a tragedy), and then an unrelenting tragedy with the familiar ones; the huge personnel from the tv show is slimmed down to Laura's immediate environment, which means no member of the Horne family, no Packards and Martells, no Sheriff Truman, his deputies and Lucy and no Big Ed & Co. Fans of these characters probably were frustrated. In addition, Cooper, who in the show is the embodiment of optimism, does appear but by the nature of the story can't be optimistic - rather like the chorus of a Greek tragedy, he's reduced to commenting and being unable to stop the disaster from happening.

All of which makes for a movie which couldn't be popular.

Footnote: an example of how the film really only works if you know the show is that the opening fifteen or so minutes are funny (and a witty satire on the show) ONLY if you're a fan, because D. Meadows where the murder of Theresa Banks happens is basically the anti-Twin Peaks. Here, the FBI agent arriving isn't greeted by a friendly sheriff and nice, excentric locals, but a hostile and corrupt sheriff, and locals who loathe him, the coffee tastes horrible and the food tastes worse; everyone is affected by the death of Laura, but nobody cares about the death of Theresa, nobody even shows up to claim her body; instead of the big Northern Hotel you have a trailer park, and so forth.