Except those historians are wrong...
?? Speculation can't be wrong...some historians have speculated .the Confederacy knew that all it really had to do was demonstrate for a bit longer in order to prevail. That's a highly valid speculation given the context of 1863, yes? The Confederate leaders were real people, not Foghorn Leghorns. Confederate leaders, Lee included, were able to "read the writing on the wall" as it were.
In any case let's admit that no prominent CW historian has speculated the Confederacy actually wanted to conquer .the North. That goal so obviously ridiculous, it's only logical to suppose that the Confederacy had an actually realistic strategy in mind: most likely that was to demonstrate for a bit longer and ride out the election cycle in the North, the tactic being to threaten Pennsylvania and Washington D.C. -- the original and the current seat of the United States government. Smart.
That's such a valid thing to suppose, given that Lincoln himself recognized the strategy and was compelled to issue the 1863 Emancipation Proclamation and black enlistments in order to stop that train. It's valid to suppose that was about the only thing that would have worked at t, tat point, and it did work. Smart.
Even as amateur historians, there's no useful purpose served in flag-waving more that a hundred fifty years after the fact.