Why were the Israelites not circumcised in the wilderness?

[TonyChanYT]

Genesis 34:

24 All the men who went out of the city gate agreed with Hamor and his son Shechem, and every male in the city was circumcised. 25Three days later, while all of them were still in pain, two of Jacob’s sons, Simeon and Levi, Dinah’s brothers, took their swords and attacked the unsuspecting city, killing every male.

Simeon and Levi took advantage of their weakness and successfully attacked the city.

Centuries later, Joshua 3:

17 The priests who carried the ark of the covenant of the LORD stopped in the middle of the Jordan and stood on dry ground, while all Israel passed by until the whole nation had completed the crossing on dry ground.

Israelites crossed the Jordan into the enemies' territories.

Joshua 5:

2 At that time the LORD said to Joshua, “Make flint knives and circumcise the Israelites again.”

These Israelites were not circumcised during the wilderness wondering.

8 And after the whole nation had been circumcised, they remained where they were in camp until they were healed.

These were their days of vulnerability. Why did God choose to circumcise the Israelites after they had crossed the Jordan River into enemies' territories?

It was a test of their faith, whether they would obey and trust God. They did, and God protected them from enemy attacks.

What is the significance that God ordered Joshua to circumcise the Israelites after they had crossed the Jordan River rather than before?

God let them be uncircumcised and didn't punish them for it so that all of them could be circumcised on this single occasion. They were all united at this point by circumcision and ready to obey God to initiate the attack on the Canaanites. Circumcision was a sign of their faith.

Similarly, before Moses returned to Egypt to take the Israelites out, God wanted to make sure that Moses' son was circumcised, Exodus 4:

24 At a lodging place on the way, the Lord met Moses and was about to kill him. 25 But Zipporah took a flint knife, cut off her son’s foreskin and touched Moses’ feet with it. “Surely you are a bridegroom of blood to me,” she said.

Circumcision was a sign of their faith.