Lando wasn’t gay in the movie. He didn’t have any sexual relationship at all with anyone. He came off as a libertine who went around the galaxy playing cards and carousing.
If you saw the movie with no preconceptions there is no way you would call him or the movie gay.
Wayyy to much being read into it, mostly by LGBT folks looking for heroes and on the other end far too sensitive conservatives looking for offenses.
It was dumb silly fun popcorn movie period.
That was directly from the writer himself, Jon Kasdan, who after receiving criticism for it took to twitter and insulted fans and admitted they were pursuing a Leftist political agenda. You can look it up.
But in any event, the low ticket sales are due to The Last Jedi - compounded by the multiple insults hurled at fans by Kasdan, Rian Johnson and their allies since that time.