When people in positions of authority, like legal experts, don’t fully grasp how easily digital content can be manipulated

Well, thing is, most people can't.

In a lawyers view, and a judge's view, some skilled expert "hackers" can, and its called hacking. (so i guess we're all hackers)

I once discussed these things with a (knowledgeable) lawyer. He explained you can just present almost anhthing in a court case, and when it isn't refuted, well then it's valid.

In a case my lawyer (same one) presented a printed out email. Other party did not claim it was false, so it's suddenly just as valid as a registered letter. (it was a genuine email).

In another unrelated case, the other party suddenly introduced a forged picture. If I hadn't been there at that moment (I wasn't supposed to actually), then suddenly it would have been proof.

Court cases are not about truth, and not about justice. They are about convincing the judge.

And judge's job is not to find the truth. It's to convince the public that ruling was just.

Well, at least for email, it's theoretically possible to prove it's authenticity through third-parties. E.g. lawyer can ask GMail "did you receive this email with this DKIM?".