You are confusing our human inability to cognate subtle, complex organization with "random chance". What little actual chance is involved is very subtle and very slight. It can only occur when a very precise balance of causation happens. And that very rarely happens.
Think of a marble clattering down an inclined plane filled with protruding pegs. We will think it's course through the pegs is "random chance", but in fact it's being completely dictated by a very common set of causes, and could be easily and accurately predicted as a result. The only way chance ever would occur would be if the marble encountered a peg at just such a precise speed and angle that the factors that would dictate that it fall to the right or left of the peg are so exactly equal that they become negligible. Meaning that they are ineffectual in causing the marble to fall to either side. Yet it falls, anyway.
Many would argue that such a condition cannot ever really happen, as there would always be some lesser causation to come into play. These people are called 'determinists'. For them, there no such thing as 'chance'. I disagree, but I recognize that chance is actually a very rare condition.