Dead People

Alma 56:11; “Nevertheless, we may console ourselves in this point, that they have died in the cause of their country and of their God, yea, and they are happy.”

Ecc. 9:5-6; “For the living know that they shall die: but the dead know not any thing, neither have they any more a reward; for the memory of them is forgotten. 6 Also their love, and their hatred, and their envy, is now perished; neither have they any more a portion for ever in any thing that is done under the sun.”

Why are dead people happy?