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Here is a few links about Redbuds.
The Pansy cultivator seems to have the exact growing pattern as you have described. Leafing low on the trunk.
Redbud has a very thin bark and care must be taken to protect in the future.

http://edis.ifas.ufl.edu/st147
https://www.gardeningknowhow.com/ornamental/trees/redbud/caring-for-redbud-trees.htm

https://www.clemson.edu/extension/horticulture/nursery/ipm/book_files/chapter_12

Redbuds bloom from nodes on the branches. After a tree has bloomed many years from the same node area, it develops swollen areas that produce seed pods, pictured here:
http://treenotes.blogspot.com/2009/07/redbud-pods-maturing.html

I couldn't find anything definitive in my research so I can only conjecture. I imagine that a tree expends a lot of energy producing seed pods and that this, in turn, may affect flowering production the following year. Also, I question what happens to the node after the seed pod process - judging by the photo, it looks to be destroyed or "spent" - in which case, no blooms would be possible.

For more information on the care of redbud trees, please visit the following link:
https://www.gardeningknowhow.com/ornamental/trees/redbud/caring-for-redbud-trees.htm

Some people consider redbud trees to be messy due to the seed pods they drop, however, there are varieties of redbuds which drop few to no seed pods, as discussed in the following article:

http://www.whatgrowsthere.com/grow/2012/02/27/redbuds-with-very-few-messy-seed-pods/

For more information on redbud trees, please visit the following link:
https://www.gardeningknowhow.com/ornamental/trees/redbud/caring-for-redbud-trees.htm

Yes, the harsh winter has been very hard on our gardens.

If the branches are brittle and snap, then most likely your tree died.
It is a good time to plant a new tree and get it established.
I lost several established trees in my zone 4 garden this year.

https://www.gardeningknowhow.com/ornamental/trees/redbud/caring-for-redbud-trees.htm

I firmly believe that the burlap should be removed prior to planting.
When large trees are planted, the bottom of the burlap should be carefully cut open with care not to cut any roots.
Then when the ball is placed in the hole the top of the burlap is opened and cut away from the root ball.
That being said it could be but not necessarily the reason your tree is losing leaves.
Is the tree receiving adequate water?
Weather stresses? Cold winter? Wind? Heavy rain?
Do you see any signs of insects or disease?

Here are a few links with more information.

https://www.gardeningknowhow.com/ornamental/trees/tgen/watering-newly-planted-tree.htm

https://www.gardeningknowhow.com/ornamental/trees/tgen/how-and-when-to-plant-trees.htm

Do the branches bend or break and snap off?
It is most likely that your newly planted tree did not survive the long harsh winter that nearly the entire United States suffered this past year.
The growth the you are seeing at the base are most likely growing from the root stock and are of a different tree origin most likely.
Most garden centers or nurseries will replace a tree in the first year if it does not survive.
It sounds like you used the proper care of the tree.

Here is a few links.

https://www.gardeningknowhow.com/ornamental/trees/redbud/caring-for-redbud-trees.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/watering-newly-planted-tree.htm