It is explained in that video. I know it, because I asked that original question.
Children of Israel had a constant source of warners (prophets) and presence of God in front of them. They were always warned orally about these things. And Talmud (which is referred to the oral Torah) does make reference to afterlife, showing how scholars who were reading the Torah were understanding the law of God.
Furthermore, the bigger question is that why would Israelite care about Divine Law if it had no serious consequences, think on that for a second. Why have a law, if it has no effect on their afterlife? Jews care too much about Law of Torah but they need to explain why do they care? What’s the gain, what’s the loss? It is referred what it is:
Multitudes who sleep in the dust of the earth will awake: some to everlasting life, others to shame and everlasting contempt. (Book of Daniel 12:2)
Furthermore, why was Hazrat Isa (PBUH) even sent if the religion was totally fine? Because Israelite sliced the religion in half. As I pointed out early, why have a law if there is no consequences? Hazrat Isa (PBUH) came to answer that, to remind the Israelite that eternal reward and punishment awaits, that is why Law of the Prophets must be followed, which is why the concept is much stronger in Christianity, it reminds Israelites which they forgotten and why Christians preach about Law being fulfilled by Atonement act i.e fulfilling the Law leads to eternal life, this is implied, meaning Israelite knew about this.
Furthermore Qur’an refers to Jews having this belief:
And they say: “The Fire shall not touch us but for a few numbered days:”
Say: “Have ye taken a promise from Allah, for He never breaks His
promise? or is it that ye say of Allah what ye do not know?” (Qur’an 2:80)
Why is a sect of Jews 1400 years ago know about a Fire? If there is no concept of afterlife in Jews, why are there sects of Jews that believe in it? Because their prophets had an oral tradition about it.
And Rabbi Yehoshua ben Levi said: These are people who are considered important [yekarim] in this world and unimportant [kefuyim] in the World-to-Come. This is like the incident involving Rav Yosef, son of Rabbi Yehoshua ben Levi, who became ill and was about to expire. When he returned to good health, his father said to him: What did you see when you were about to die? He said to him: I saw an inverted world. Those above, i.e., those who are considered important in this world, were below, insignificant, while those below, i.e., those who are insignificant in this world, were above. He said to him: My son, you have seen a clear world. The world you have seen is the true world, as in that world people’s standings befit them. (Pesachim 50a) https://www.sefaria.org/Pesachim.50a.6?lang=bi
Say: “If an afterlife with God is to be for you alone, to the exclusion
of all other people, then. you should long for death-if what you say is
true!” (Qur’an 2:94)
And they say, “None will enter
Paradise except one who is a Jew or a Christian.” That is [merely] their
wishful thinking, Say, “Produce your proof, if you should be truthful.” (Qur’an 2:111)
So apparently there are Jews who believe in afterlife, if the claim that there is no afterlife and all in previous religion, where are these people in time of Prophet (PBUH) getting their concepts from? If not oral tradition? Same way our Sunnah to us?
And even if one wants to insist that there is no such concept of previous religion, it doesn’t explain how you people answer life’s questions, where we come from, our morality, what happens after death etc. These questions can only be answered by these major concepts, that’s why they have always existed in every time period, anything less won’t satisfy religious narrative as I pointed out early, why cling to a Torah Law if there is no serious consequences? Because the Jews knew that the Law from God did affect their Afterlife.
Qur’an is however very clear, and more clear than Christians sources because there is no going be no warners to come. They needs to function as a book and a prophet. Before Qur’an, they were prophets who were talking about Paradise, Hell and all, we know it because people in time of Prophet (PBUH) were discussing them, it was essential for them to discuss it because when a new prophet arrives, their afterlife gets affected otherwise why would Jews want to oppose Prophet (PBUH) or disagree with him if there was no Hell for them at all?
sefaria.org
Pesachim 50a:6
And Rabbi Yehoshua ben Levi said: These are people who are considered important [yekarim] in this world and unimportant [kefuyim] in the World-to-Come. This is...