[dakara] is a connector meaning because. [koso] adds emphasis.
科学者だから、分かりました He is a scholar, so he understood
科学者だからこそ、分かりました (only because) he is a scholar, he was able to understand
Note that [dakarakoso] is not usually (cannot be?) used to give a negative emphasis. You would not say that you *didn't* do something especially because of a particular reason.
I think the english explanation for this grammar point should be "especially because of..." to avoid confusion with [arebakoso], which has a stronger sense of highlighting an exclusive reason.
One other thing - I think this entry should be changed to "karakoso", since the "da" copula is used only connect karakoso with a noun or noun adjective (or to refer back to a previous sentence, as in examples ,  and ). You can use karakoso after verbs and い adjectives as well.
I think the important thing is that it's a direct form, whether perfective or imperfective (and whether positive or negative, as I recall) plus から. As opposed to a gerund form which gives the meaning of a sequence of events (AてからB, " after A, B (happened)") instead of giving causality.
As for the こそ part, doesn't that have it's own page yet? Seems like it'd make sense to separate that from the rest of the pattern, or just make a note about "if using こそ it follows the から"