It looks like it may be planted too close to the house. Not sure of the cultivar but there is a good change that this tree will grow 8ft wide and equally tall. No it is not an option to just prune it.
It looks like the hostas are ok. Remove the 6" of mulch (a little too much 2-3" is good.) put your hand into the soil and see if it is wet , dry , damp. I might guess that this plant needed water at one point and maybe just reacted by dropping leaves. Not unusual. Test the bark - scratch bark to see if there is life - green under brown bark.
Wait till next year before you remove - it may bud up in the spring.
Mike