Endless, rambling discourse made up of innumerable anecdotes, each more fascinating than the last.... Krashen has amazing stamina. You sense a real generosity with his time and experience in giving to others which is a joy to witess.
I studied classics (Latin and Greek) at a university and got nowhere with those languages in terms of being able to read them proficiently in spite of getting straight As. All they did was drill and test grammar and translation. A decade later I can read Aristotle in the original comfortably. What it took was ditching the grammar books and just reading extensively in the language and focusing only on comprehension. Language and its acquisition is a biological system. You have to just let it do its work. You cannot force it.
I don't know how old this video is. You state that you've been preaching "comprehensible input" for 30 years. But circa 1982 at SFSU you were a major component of the TEFL/TEST Masters program that I did. Whereas 20 years ago when I came back to the US, I thought my whole MA had become meaningless. It takes something like RU-vid to enable us to get back in touch with what we have tested in our actual careers as teachers. Just in the last few days I have watched RU-vid videos wherein younger linguistic academics repeat and repeat the importance of Comprehensible Input.
Sophia's case doesn't make any sense, more explanation is needed. I think i know what you had failed to mention. In Los Angeles they used to have so called Bilingual school education for Hispanic Students. They took English as ESL class BUT all the other classes were in Spanish. It was a TERRIBLE FAILURE, all those Hispanic students geaduated without learning any English. Some were US born and raised (in Hispanic families) and they didn't speak any English after graduating a Los Angeles high school.