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ELI5: why do some ice pops crystallize while others just become rock solid?

Hello,

So recently I’ve fallen back in love with ice pops but noticed that some of them are solid through and through while others are almost as if they have developed crystal structures within it.

I thought it was because of sugar but the amount is comparable between the 2 with them having about the same sugar content.

What could be causing it to form into those crystalline consistency and is there a way to replicate it?
gpt
theres 3 factors here. 

First is the rate of frezing. 

A slow freezing process will produce larger crystals, while a faster freezing will produce smaller crystals with a smoother texture, thats why its recommended that you cool down food to pre freezing temperatures (especially meat) so the freezing process is shorter. 

The second is Agitation.  
Ice cream is churned, meaning its moved constantly and mixed to make sure ice crystals are distributed uniformly over the the mass of the liquid being frozen and breaking crystals that are growing too big, mantaining a smooth tecture.   

The third is impurities.   
Icecream has several things mixed in to it which modify the texutre, fats, sugars, air, the air bubbles give it a smoother texture, the sugars interrupt the size of the ice crystals and the fats give you a different texture which limits the packing of the ice crystals. 

Also an interesting thing about this is that in the making of many soft candies these 3 factors come in to play, the amount of water in a sugar mixture defines how hard a piece of candy will get, in toffee the mixture is agitated to put air in to it as to soften it and in many mashmellow recipies, the addition of a different sugar type (fructose) is added to disrupt the sugar crystal formation allowing a softer texture.