Basically, conservatives do not have much faith in the ability of people to devise perfect worlds. They think that human beings are inherently fallible and prone to error. Because of this, they prefer the status quo and they prefer not to have radical change.
So how does that go together? How does believing that people are fallible lead to that?
Conservatives believe that the whole mass of people are less likely to be wrong than individuals. They believe that people are less likely to be wrong in the long term than in the short term. Therefore, the way things have always been done is probably right and we should not depart from it too easily or quickly.
Conservatives believe that when we try to change quickly or radically, we are throwing away the wisdom of all the people who have come before us. Instead of heeding them, we are assuming that we know best. Because conservatives think that people are more likely to be wrong short term than long term, they think we should be more humble and we should accept that the old ways are probably there for a reason.
I am including a link to a discussion of Edmund Burke's writing on the French Revolution, which is a classic of conservative thought. As that discussion says, Burke and conservatives argue that
If every human institution were not the best of its kind, then the institution would have evolved otherwise. This vision reflects an innate pragmatism that trusts no a priori judgments and leaves all arrangements to be forged in experience.