The shrub was probably planted the old way - dig a hole, take it out of the pot, bury it and maybe add a little extra dirt. This results in a plant that continues to be root bound and suffocating from the extra dirt.
Shrubs, like trees, have a natural line where the bole or stem needs to be above soil, but many nursery stock in black pots was way down in the pot so they usually shovel in more dirt to make it look like there are more roots.
When you take a plant out of the pot you need to brush off the top dirt until you get to the roots, the real roots, not the little birdsnest of adventitious roots that can form in that upper dirt layer.
Your plant can be helped in a number of ways, if this is the case. Carefully pull the soil back from the plant until you reach the root flare, or the point where the large roots extent horizontally from the plant. This is the level that should remain exposed. You may want to carefully poke around and see if there are circling or girdling roots to trim. If it is like some potted transplants, it might even be possible to dig it up, trim the girdling roots, pull the rest of the roots outward, and stake them down on the area where it will be replanted. Don't replant it deep, make the hole shallow and wide.
Here is how to bare root plants.
Also, sometimes using part of the
Sick Tree Treatment around shrubs can help.