J. Warner Wallace, author of Cold Case Christianity, states that he has, “never had a case where two witnesses have ever agreed completely… [he’s] come to expect some degree of resolvable variation in true, reliable eyewitness accounts.”
In criminal investigations, testimony from two or more witnesses telling the same basic story, but with some variations, is considered reliable. By contrast, when eyewitness accounts are identical, witnesses are suspected to be colluding, possibly even lying.
If they had wanted, the gospel writers had ample opportunity to alter their stories so as to be in complete alignment with each other. But, they were confident they were telling the truth and left their accounts as-is.