>>21448805Cocoa powder contains a tough mix of both hydrophilic starch particles and hydrophobic fat molecules that make it nearly impossible to mix completely with milk at room/refrigerated temps without clumps unless you spend a lot of time and mechanical action to force the solute to dissolve in solution. A blender's high-rate of speed also helps the cocoa to remain in suspension longer before falling out and settling in the bottom of your drinking vessel in a process known as sedimentation (commercial chocolate milks overcome this with emulsifiers like carrageenan you often see on the ingredients label that also acts as a thickener since they tend to use skim milk for the base as a cost-saving measure).
https://www.youtube.com/watch?v=CgX_xuCMsqM
https://foodcrumbles.com/chocolate-milk-sedimentation/
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