The story of what happened is well known. Apart from Joshua and Caleb, ten of the twelve spies came back with a pessimistic report, and the tragic consequences caused a long delay before the people’s final entry to the land.
Yet lo and behold, when the entry to the land was imminent, the new leader, Joshua, sent a fresh investigating team. How could he do such a thing when he must have had vivid memories of the disaster that the spies had caused in Moses’ time?
The 19th century commentator, Malbim, says there were several differences between the two investigations.
Moses’ spies were sent at the request of the people and reported back to them; Joshua commissioned his team on his own without the people’s involvement. Moses’ investigation took place long before the people were near Eretz Yisra’el and the people didn’t completely understand what was going on. Moses sent spies to check whether the land could be conquered; Joshua sent spies to ascertain how it could be conquered.
Moses’ investigation was dramatic and the spies set off with public fanfare; Joshua’s representatives went quietly without a fuss.