This main focus of this craze in the media was the parents trying to purchase this item for their children, leading to numerous fights and riots between customers when supplies ran low.

▲从形式上看，划线部分有两种理解：一是按你的理解，将其分析为动名词的复合结构；二是将 trying…分析为现在分词短语作定语，修饰 the parents。但考虑到后面的 leading to…是个结果状语，说明前面讲述的肯定是个事件（而不会是人），因为从逻辑上看，只有某事件才会导致某结果，而某人是不会导致某结果的。所以你的理解是对的，应将the parents trying to purchase this item for their children分析为动名词的复合结构。

▲句子分析：

主语：This main focus of this craze in the media（其实包括主语和修饰它的定语）

系动词：was

表语：the parents trying to purchase this item for their children

结果状语：leading to numerous fights and riots between customers when supplies ran low，修饰前面的动名词短语，即是“因为父母争相购买”才导致了后面的这个结果。

▲句子大意：媒体对这个爆款商品的主要关注点在于父母都争相为孩子购买这样东西，结果当供应出现不足的时候，导致了购买者之间的打斗和骚乱。