The word pudisteis is the preterite form of poder in the second person plural.
See the full poder conjugation

poder

Supongo que todo es posible si tú y Lyle pudisteis salir.
I guess anything is possible if you and Lyle could get out.
Por eso es que no pudisteis encontrar el dinero.
That's why you couldn't find the money.
Entiendo que mamá y tú no pudisteis hacer que funcionara.
I understand that you and Mom couldn't make it work.
Bueno, supongo que no pudisteis cambiar el pasado...
Well, I guess you can't change the past...
Bueno, supongo que no pudisteis cambiar el pasado...
Well, I guess you can't change the past...
No pudisteis controlar mi mente antes, y no podréis ahora.
You couldn't control my mind before and you can't control it now.
Da igual, ¿pudisteis contactar con Marilyn en el mundo de los espíritus?
Anyway, were you able to contact Marilyn in the spirit world?
Supongo que pudisteis coincidir en un restaurante.
I suppose you could've met at a restaurant.
Espera, ¿no fue así o no pudisteis?
Wait, it wasn't like that, or you couldn't?
Y dime, ¿pudisteis encontrarla?
And tell me, were you able to find it?
Supongo que no os pudisteis quedar en el carro.
I guess you couldn't stay with the carriage the way it was.
¿No pudisteis convencerla para que no testificara?
You couldn't convince her not to testify?
No pudisteis meter el elefante en el coche, eh?
Couldn't get the elephant into the car, eh?
Pero no pudisteis vivir juntos.
But you couldn't live together.
Entonces, ¿por qué no pudisteis salvarla?
Then why couldn't you save her?
¿No pudisteis convencerla para que no testificara?
You couldn't convince her not to testify?
Yo... lo hicisteis lo mejor que pudisteis.
I... you did the best you could.
Ese sonido que no lo pudisteis olvidar.
That sound you couldn't forget.
Parece que no pudisteis hacer nada.
Looks like there was nothing you could have done.
Y alimentasteis vuestros vientres. ¿Cómo pudisteis?
And fed your bellies. How could you?
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