The only honest answer to this question is that it simply wasn't an issue prior to this election cycle. The modern primary and ballot systems are designed around 1940s technology: the printing press as the dominant source of political information; trains as the most efficient travel for delegates, candidates, and political entourages; in-person discussion as the most effective form of decision-making. State systems are locked into this mode because (in general) our deeply antagonistic two-party system makes everyone risk-averse. Change is bad: it messes up calculations when everyone is struggling to grab that half-percentage point advantage. But that 1940s mode also meant that everyone allowed a certain amount of slack. States might set deadlines, but if a key event ran into a scheduling problem (due to weather, transportation delays, challenges, tallying issues, etc), states would just (metaphorically) twiddle their thumbs and wait. Most likely they would lay out the ballot printing form — yeah, remember, they did typesetting by hand back then — with the prospective candidates names (or with fillers) and not run any copies until the convention was over and the candidates confirmed.
Everyone expected that things would occasionally go awry, and no one worried about it overmuch. They all bowed more or less gracefully to the inevitable inconsistencies of the world.
It's only in the last election cycle or so that political parties have started to weaponize electoral policy, trying to turn loose deadlines into tight ones for their party's benefit. It's a sign, I think, of increasing disrespect in parts of the political class for democratic principles; a desire to achieve power by carving out solidified voter blocks, not by attracting voters. I mean, the point of these deadlines is to get the candidates' names early enough for government work, not to create a 'gotcha' condition, but that's lost on far too many partisans these days. So states are suddenly finding their 'soft' policies confronted by hard-line attitudes, and — as states are prone to do — are stumbling and fumbling to try to find solutions.
