Joshua 5:4

Now this is why he did so: All those who came out of Egypt—all the men of military age—died in the wilderness on the way after leaving Egypt.

This is the reason Joshua circumcised them: All the people who came out of Egypt who were males—all the men of war—had died in the wilderness along the way after they had come out of Egypt.

Joshua had to circumcise them because all the men who were old enough to fight in battle when they left Egypt had died in the wilderness.

This is the reason why Joshua circumcised all the people: all the males who went out from Egypt, all the warriors, died in the wilderness as they went out from Egypt on the journey.

And this is the cause why Joshua did circumcise: All the people that came out of Egypt, that were males, even all the men of war, died in the wilderness by the way, after they came out of Egypt.