Sheldon's own hubris is also kind of to blame for what happened immediately after they got home from the North Pole....
Their plan was to tell him once they were back before he made any announcements. I think it got to a point where Leonard, Howard, and Raj saw that the experiment was going to be a failure, but they would still be stuck up there with Sheldon.
Meanwhile Sheldon was getting exponentially more frustrated and difficult to deal with, refusing to accept failure. So they did it just to make the rest of the expedition bearable and then they almost immediately came clean about it all (well, I do believe Leonard was going to but then Penny jumped his bones, so Raj and Howard took care of it). But Sheldon had jumped the gun and already announced it. FYI, it's very reasonable for the three of them to assume they'd have time to come clean about it before word got out.
Sheldon however should have known much better than to make giant conclusions based on partial data. Very sloppy by him. He didn’t even check for alternatives. It's highly unprofessional to make mass announcements about a discovery before data is truly analyzed and an official paper is written and published, but Sheldon is such a self-promoting narcissist that he couldn't keep it to himself.
And the conclusion he made (BEFORE adequately reviewing his data and running more subsequent tests which any decent scientist should know is a big no no) was a narcissistic doozy!
Thinking he had solved string theory.