The events that I had attended were well organized and were highly entertaining in many ways.

well 在这里是副词，表示"很好地、令人满意地"，用来修饰后面的形容词 organized。 organized 是动词 organize 的过去分词形式，表示"被组织、被安排"的意思。organize 由词根 organ（器官、组织）和动词后缀 -ize 组成，本义是"使形成有机整体"。 well organized 这个短语表示"组织得当的、安排有序的"，用来形容活动或事情被精心策划和安排。