Q.Magnolia shrub “Susan”
New this year and never quite made it – just a couple of very weak leaves today. I had it planted in a local park for my friend’s sister “Susan” who died in April and I couldn’t feel worse about it !
I'm not sure what went wrong with your Magnolia; but understand the stress of losing a new planting.
A consistent watering regimen is needed immediately following planting to ensure your new tree remains healthy and adapts to its new home.
This article will help you review the care.
https://www.gardeningknowhow.com/ornamental/trees/magnolia/magnolia-tree-care.htm