When we see something that's considered a fact, we assume that since it's factual, most, if not all people, will see it just like us. However, it usually doesn't work out that way. Many times, even if people agree on the facts, the conclusions they draw, or what it means, can vary widely and even lead to serious disagreements. Why is this?
What is a fact?
Meriam-Webster defines a fact as:
1a : something that has actual existence Example: space exploration is now a fact
b : an actual occurrence Example: prove the fact of damage
2 : a piece of information presented as having objective reality Example: These are the hard facts of the case.
3 : the quality of being actual : actuality a question of fact hinges on evidence
Why are there differences?
From here, we can elaborate on the initial question and ask, why do people interpret "actual existence" differently. Broadly, the cultures we grow up in shape our views and the wiring of our brains doesn't care what's factual, only that we are safe from threats. While there are many other details regarding why we interpret fact differently, these two are largely responsible for the phenomenon.
The cultures we grow up in shape our values and thus how we see things. People from individualistic cultures see the world very differently than those in collectivist cultures. The "fact" that a man decided not to marry or have kids can be looked at as very negative in a collectivist culture where children are expected to get married, have kids, and have the children take care of the parents when they are older. In a western culture, this fact could still be perceived as negative, particularly within a more traditional family, but could also be seen as neutral or even positive.
In China, hot water is regularly drunk and cold water avoided. In America, we'd likely be disgusted at the thought of drinking hot water and prefer our water cold. These aren't genetic differences, but purely cultural. Sub-cultures within cultures also have different value systems and react according to those values. For example, someone who values modern art may spend a large sum of money on a piece of artwork. Someone else who values professional sports may spend a large sum of money on a Super Bowl ticket. The money spent isn't justified by any intrinsic quality, but only by what values the buyer has within. So, if a headline reads, "Modern Art collector spends $5000 on piece of art," the person who doesn't value modern art may say, "What an idiot. It looks like something my 5-year old could do." Similarly, if a headline reads, "Average cost of Super Bowl tickets rises to $5000," the person who doesn't value sports may say, "What a bunch of idiots. They pay that much to see grown man tackle each other to the ground." The headlines are interpreted based upon personal and cultural values, not on the inherent veracity of the situation.
We generally adopt the values and worldview of particular culture or subculture as a way of belonging to a tribe. We are social animals and culture bonds us together. We take on the customs and views of our tribe so that we can attain some level of status and to belong.
Our brains developed in a much different environment than the one we live in today. We didn't always have civilization. We lived in tribes in the wilderness and life was tough. We couldn't afford to be wrong about whether someone or something was a threat, so it matters more that we perceived threats than that we perceived things accurately. It's why we might get startled when we see the shape of something that looks like a poisonous snake even if it isn't. If we jump and it isn't a snake, no big deal. We can laugh about it and move on. If it was a poisonous snake and we get too close while we are trying to figure out if it is really a snake, then we might not live through it. Our brains care about protecting us, not whether we are factually correct.
Because of this hard-wiring, we can see the world very differently from others as well as from how it actually is. Another word for "jumping to conclusions" is "heuristics." Our brains rely upon heuristics to help us not spend too much time or energy on things in a world that is constantly moving and changing. Our brains just want to be right enough so that we survive. One common heuristic comes into play when we support a particular political candidate. Once we decide they are "our guy," anything they do or say is seen through a particularly favorable light. In social psychology, this is called the "halo effect." Even if someone acts like a devil, we can easily use the halo effect to interpret it innocently or even favorably. This happens not just with politicians but with friends and family, too.
Another common heuristic is called the fundamental attribution error. It means that most of the time, we interpret behaviors of other people as if the action is based upon who they are as a person rather than the particular situation. For example, someone who cuts you off on the freeway many times is considered a rude jerk, rather than someone who has diarrhea and needs to get to the bathroom. However, most of the time, behavior is contextual, or situational rather than from an inherent trait.
People see the world very differently from one another. This also includes things like facts. Even if we agree that something happened, what we make of it can vary greatly. Our culture and values influence what we "see." We also are under the influence of many heuristics which are hard-wired in our brains so that we can avoid threats quickly even if we aren't seeing reality clearly. The combination of all these factors distorts our views and influences our reactions all in the name of surviving an unpredictable world. Continuing to fit in with our tribe by taking on their views is also a protective instinct.