The scuba diver who was attacked by a shark was rushed to the hospital. 此句為何可以有兩個was共存？

本句是一個complex sentence，有主要子句和附屬子句。附屬子句是用來修飾主要子句主詞的形容詞子句。
was attacked 是「附屬子句」的動詞
was rushed是「主要子句」的動詞
兩者都是被動態，其中的was是助動詞，幫助後面的主要動詞形成被動態（be + p.p.)。

句子結合描述發生在這個scuba diver潛水員的兩個情況，用了加插/附加句子成為組合句。
情況1
The scuba diver was attacked by a shark.
The scuba diver was rushed to the hospital.
這兩行動中句子的重點是"送去醫院"，但同時交代說明"為何要送去醫院"，所以要加插/附加"描述"這人受傷的原因。
The scuba diver (who was attacked by a shark) was rushed to the hospital.
假如這加插/附加的描述是跟主意思的句沒有直接關係，(XXXX)這句其實是要用,XXX,分隔的，但這句由於"被送去醫院"跟"被鯊魚攻擊"是有直接關係，所以句法上便不會加","。
但是假如再加強描述這scuba diver其實是有十年潛水經驗，那麼這類描述便要留意","的必要，句子寫法上亦可能會改變。

The scuba diver, who has ten years diving experience, was attacked by a shark and was rushed to the hospital.