Meaning of "It's easy when you're done" in a dialogue?

Question

there was a conversation on a stack and there were some comments, I could not relate to each other.

First person commenting on the text : Do you have any reference to an easy in-place implementation of the merge step in mergesort? (just curious)

text owner: I haven't checked these, but they popped up when I searched. (some links ....)

First person Okay, so easy is in the eye of the beholder. It's easy when you're done.**

I know that in the eye of beholder means that, being easy looks different to every person, but what does It's easy when you're done from the same line? or maybe the whole last comment.

Answer 1

Q.

Meaning of “It's easy when you're done”

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A. After you have completed a task, (particularly one that seemed difficult at the time). Now looking back the task seems an easy one. (because now you know how to do it).

Answer 2

It's easy when you're done.

It means that it looks easy when the problem is already solved/code is already written etc but might not looks that easy when the problem was unsolved.