An album doesn't need ten singles and Invincible was never going to have that many lmao. 3-4 singles were the norm at the time. 'N Sync's No Strings Attached, Backstreet Boys' Black and Blue, and Britney Spears' Oops, I Did It Again all came out in 2000, just a year before Invincible, and none had more than four singles. Each of these albums sold over 15 million worldwide.
Some people think Sony sabotaged the album by not releasing "You Rock My World" as a CD single in America, but this is nonsense as it was common for record labels not to release songs as CD singles at the time. By 2001, it wasn't necessary for a song to be a CD single to be a big hit on the Hot 100; in 2000, "Bye Bye Bye" by 'N Sync hit no.4, "Kryptonite" by 3 Doors Down hit no.3, and "Try Again" by Aaliyah hit no.1 (the first song in history to hit number one solely through airplay). In 2001, "Differences" by Ginuwine hit no.4, "Let Me Blow Your Mind" by Eve hit no.2, "Angel" by Shaggy hit no.1, and "Lady Marmalade" by Christina Aguilera, Lil' Kim, Mýa, and Pink hit no.1, "Falling" by Alicia Keys hit no.1, and "U Got It Bad" by Usher hit no.1. All of these songs exceeded the top five without a release as a CD single. "You Rock My World", on the other hand, only hit no.10. "Butterflies" did even worse, only hitting no.14. Not having a CD single wasn't any excuse; the fact is, these songs just weren't very popular.
Sure, Sony could have at least released "Butterflies" and one more single worldwide ("Cry" should have never come out, period), not to mention air a commercial for the album during the 30th-anniversary concert broadcast that over 30 million people watched, but would the album have really sold much more? It sold about 6 million; even if the promotion went well, I don't see it selling more than double that amount. Funnily enough, the album was purported to have sold over 12 million in the past and even back then, that number was considered disappointing. All things considered, though, Invincible didn't do that badly for a 2001 pop album. Britney by Britney Spears only sold about 8 million worldwide and none of its singles were very successful. Celebrity by 'N Sync only sold about 6 million and most of its singles weren't that successful, either. In 2001, people were just burnt out with pop music.