First of all if you don't know the reason why it takes 40 years for moses and Israelites to reach the promise land just read the bible, and don't mislead everyone by your joke

Secondly base of my memories in reading the Bible if it doesn't betray me, here's the reasons why it take 40 years for moses and Israelites to reach the promise land as follow:

1. Moses need to a detour to his father in law for his achievement in freeing his people
2. Moses must visit the mountain where God call him to the save his people and get the 10 holy commandments and government system for Israel which God made from a stone tablet that take a couple of days
3. Moses father in law advice and help moses to organize his clan so that he will not be overburdened by his responsibility
4. Moses divide the responsibility in each clan and assign Levites as priest and the instruct them in how to proper way to worship God and how to proper way to give offering to Him
5. All the israel clans making the ark of the covenant and other religious materials and equipment
6. After the incident on how half of the clan of Israel betray God and moses. God was so furious that he plan to kill them all, and let moses and his family lived and start a new plan from scratch. However, moses plead to God spare them and don't let other people say that God free Israel from Egypt slavery just get killed in the desert. After God incline His ear to moses and hear his plead God consider it and just let the old generation sie and only the new generation can see the promise land
7. God was pissed with the Israelites because they are always complaining about on food, water, not following His instructions from moses, and always comparing their live as slave in Egypt and how great it was than to be free and following moses and to their God
8. Moses, aaron, and mariam was not able to go to the promise land because moses have sinned against God due to being cocky about the water from the stone and didn't say that God provide them water through Him. Aaron and mariam was not able to go the promise land because they become entitled and try to betray moses which God was furious which also delay their travel
9. Israelite have several battle with other clans which God also trained them to become a battle harden wariors dor prepared of claiming the holy land of Israel
10. Due to Moses sin was not able to go to the holy land but only see from the distance. God instruct moses to train someone to become his successor which is Joshua.
11. Before Israel can enter the land moses assign 12 spies to investigate the holy land. Which also take time and discussion to every clan leaders in each tribe of Israel. 10 spies report disheartening news because of lack of faith and bring fear to the Israelites and 2 spies report good news which encourage Israelites to claim the land which God have promise to their forefather