Redbud trees can have problems with pests and diseases but usually when a recently planted one dies the problem can often be traced to improper planting or mulching. When the tree is planted, care must be taken to insure that it isn’t buried too deep with dirt against the trunk.  Where the soil came to on the trunk of the tree when you purchased it need to be still visible after planting.  If the hole is dug too deep or soil is piled up too high on the trunk, it slowly smothers the tree .  Likewise piling mulch up against the bark of the tree prevents the flow of moisture and nutrients up the trunk to the branches slowly killing the tree.  “Volcano mulching” is very popular lately but will eventually kill even very large trees.  More on proper planting HERE:  https://blog.timesunion.com/gardening/plant-it-correctly-for-a-healthy-life/7444/

More on the evils of volcano mulching HERE: https://extension.psu.edu/mulch-volcanoes-are-erupting-everywhere