Marriage is a strong relationship between to couples man and woman, according to the bible, this relationship is only valid when the two couples are still alive but if one dies the relationship is assumed to have also die. When one spouse dies, that marriage bond ends. The living husband or wife is no longer tied to that relationship.
Because of death, marriage after death of spouse is allowed and acceptable by God and God doesn't see it as a sin. Instead, it shows that the person is free to start a new marriage if they choose to.
The Bible understands that people need love, care, and companionship. After losing a spouse, it can be hard to live alone. Remarriage can bring comfort, support, and a new beginning, and this is accepted.