the law then was if your brother died and left a widow then you have to marry her and her 1st born will still be of your brothers line. he decided to not follow gods law. hence death.

we also need to undrstand that after jesus were under the new laws. no longer are men to have muti wifes. after jesus death were under the new covnent. Thats why we do NOT do burnt offerings anylonger ( jesus was the perfect offering to atone for our sins wich adom has passed to us)