1. There is a dispute about whether one who bakes on Yom Tov for the sake of a weekday is punished with Malkus.
2. Rav Chisda agrees with Rabah in cases where his reasoning results in a stringent ruling.
3. Rebbi Yochanan refused to teach Rebbi Simlai about the lineage that was based on Divrei ha'Yamim.
4. The Rabanan eventually hid or forgot the information regarding lineage (see #3).
5. Mar Zutra lamented this loss (#4).
A BIT MORE
1. Rabah: He does not receive Malkus, because if unexpected guests would arrive on Yom Tov he could serve them the food. (Therefore, his cooking is potentially for consumption on Yom Tov.) Rav Chisda: He receives Malkus, and we do not take into account the possibility that unexpected guests may arrive.
2. Accordingly, Rav Chisda agrees that this causes a Korban Pesach to become invalid.
3. Rebbi Yochanan did not want to share this information with Rebbi Simlai either because Rebbi Simlai was from a place where many people did not have good lineage or for other reasons (see Rashi).
4. This caused them to also forget the Torah that was associated with this information.
5. Mar Zutra pointed out that there was a massive amount to be derived just from the verses that were between the two verses in Divrei ha'Yamim (I, chapters 8-9) regarding the sons of Atzel.