The inhabitants are too powerful. Although Hashem had promised the Jewish people that they would inherit the land, the meraglim questioned Hashem's credibility. This was their sin. Calev and Yehoshua tried to salvage the situation by assuring the Jewish people that the inhabitants were easily defeated. On the contrary, everyone knows that he will get a bigger piece.
Big challenges mean big rewards.
I have so much to review for the test and so little time. But we've been fighting for so long. These are big challenges for us, kinderlach. But we know the reward is great. The meraglim were punished for speaking badly about Hashem and the Land of Israel.