Why didn't Pro heroes help NightEye

Question

First of all, i didn't read the manga, so if the answer to this is a spoiler, please abstain or mark it as a spoiler so i can avoid it.

My question itself is a spoiler for those who didn't see Season 4 yet:

As we have seen in season 4, NightEye was gravely injured, survived long enough to be put in a hospital, until he died. Why didn't pro heroes use Eri quirk to save him ? rewind can cure his injury. If you say "Eri was sick", why didn't they bring Neito Monoma, the kid with the Copy quirk ? he can copy Eri rewind and save NightEye, it's not like it's going to take a whole day.

Edit: Also Aizawa was present to cancel the quirk if it gets out of control

Answer 1

Neito Monoma couldn't use Eri's Quirk, because it is not compatible with his own Quirk.

Although Neito Monoma can indeed copy any Quirk, he only copies them in their "base" state. We could say Neito Monoma obtains the Quirk as if he was a baby and the Quirk manifested for the first time.

When Neito Monoma tried to copy Deku's Quirk, he found himself devoid of any super-strength. As he explains himself in Chapter 217, since Neito copies Quirks in their base state, any Quirk that needs to charge up or stock something over time to function is useless to him. He correctly guessed that Deku's Quirk only stockpiled strength over time and didn't simply grant him super-strength. Similarly, Neito Monoma cannot use Fat Gum's Quirk as it relies on cultivated reserves of fat to function.

We have seen that Eri's Quirk, Rewind, depends on the length of her horn to function. As she uses her power, she depletes her reserves and her horn gradually shrinks. This means she had to grow and cultivate that horn to use her power ; in other words, Rewind needs to stockpile something to function.

Since Neito Monoma's copied Quirks can only for only 10 minutes at most, he absolutely does not have the time to stockpile whatever Eri needs to activate her Quirk.

Answer 2

As seen in the Anime, Eri can not yet control her quirk which is also why she is in quarantine.

For Neito Monoma, his wiki entry says the following:

Neito only requires to touch as little as a few strands of hair from the target for his Quirk to take effect. After contact with a target is made, Neito gains full access to their Quirk, at least at a basic level; it's unknown if Neito is also capable of copying further improvements that one may achieve with their Quirk.

So we do not exactly know if it would work. But they could have tried yes. Maybe it will be explored later (non manga reader here).