New research suggests our brains find it easier to just accept something is true rather than expend the effort to decide whether the information is accurate. Additionally, if the subject isn't something we care about, we're more like to accept something as true.
From Psychology Today:
If the subject isn't very important to you or you have other things on your mind, misinformation is more likely to take hold, according to the researchers. They point out that rejecting false information requires more cognitive effort than just taking it in. That is, weighing how plausible a message is, or assessing the reliability of its source, is more difficult, cognitively, than simply accepting that the message is true. In short, it takes more mental work. And if the topic isn't very important to you or you have other things on your mind, the misinformation is more likely to take hold.
Moreover, when you do take the time to valuate a claim or allegation, you're likely to pay attention just to a limited number of features, the study found. For example: Does the information fit with other things you already believe? Does it make a coherent story with what you already know? Does it come from a credible source? And do others believe it?