Reb Yochanan ben Zakai’s teaching about our relationship with the בית המקדש

Why did ר׳ יוחנן בן זכאי enact 2 traditions in one day - shaking the lulav for 7 days and refrain from eating חדש till the end of the 16th of Nissan? Fascinating insight into our relationship with the בית המקדש