If the conclusion is that obvious, why do so many scientists believe in evolution ?

Might it be that evolutionists look at their evidence with presupposed conclusions ?

This is not unheard of among scientists..
But observation, no matter how convinceing , does not presuppose conclusion...
For example, a person researching laser physics could insist that light is a wave, similar to a sound wave,
because light often behaves like a wave..
However, his conclusion would be incomplete because the evidence also indicates that light behaves as a group of particles, known a photons.

Similarly, thoses who insist that evolution is a fact base their conclusions on only part of the evidence,
and they allow their own presupposed conclusions to influence the way they view evidence..
I find it amazing that anyone accepts the theory of evolution as fact when evolutionary " experts " themselves argue,
over how it is supposed to have happened..

For example,
would you accept arithmetic as a proved fact if some experts said that 2 plus 2 equals 4,
while other experts said it was believed to total 3 or possibly 6?

If the role of science is to accept only what can be proved, tested, and reproduced,
then the theory that all life evolved from a common ancestor is not a scientific fact.