What had God done for Israel before they were ready to enter the promised land?
God had miraculously brought Israel out, gathered them as a nation at Mount Sinai amid fire and thunder, given them the tabernacle, and established their leader. He substantiated everything before they entered the promised land, promising to drive out the Canaanites Himself, using hornets to chase them, so Israel only had to move in.
Les explains that every step of the way God moved in miraculously, bringing Israel down to Mount Sinai with fire and thunder on the mountain. Israel was given the tabernacle, and everything was ready to go into the promised land. God had brought them out, gelled them as a nation of people, given them their leader, and substantiated everything. When they wanted spies, God condescended, but the spies came back with a horrible report, saying the Canaanites were too big to drive out. Yet God said He would drive them out, using hornets to chase them, and all Israel had to do was move in and take what was there. Instead, Israel wept and wailed, observing their first Tisha B'Av.