Lore Question about Goliaths

So, I actually have a weird lore question to ask. Obviously corruption Goliaths are really huge, but how exactly are they so big? Are they just... really huge guys that were zombified, or were they normal sized and the corruption just made them bigger?

 

My guess is that the corruption enlarged them as it has been known to warp bodies in different ways. It also could be that they are the result of corrupted amalgamation where multiple raised corpses were fused together, forming a larger single mass.