句中不定式的使用方法

The government officials were unprepared for some of those returning on the evacuation flights to have been stranded for so long that their original flights made them eligible for free hotel quarantine.

我了解to have been stranded是做those的后置定語，那樣請問：

1. 這個不定式表示的狀況發生在return之前還是謂語動詞were unprepared之前呢？

2. 為何不需要having been stranded，從而和returning維持一致呢？

謝謝回答

The government officials were unprepared for some of those returning on the evacuation flights to have been stranded for so long that their original flights made them eligible for free hotel quarantine.
1. were unprepared for ：沒預料到；沒籌備到
2. some of those returning on the evacuation flights：returning on the evacuation flights （乘坐撤離航班返回的）目前分詞作 some of those（人）的定語。
3. the evacuation flights to have been stranded for so long：to have been stranded for so long 不定式作 the evacuation flights 的定語，完成體表示 “航班被滯留” 的時間早于 returning。
4. that their original flights made them eligible for free hotel quarantine：結果狀語從句。