Bishop Ushher did not understand Hebrew and based his calculations on what he thought the translation into English signified.
Second, religious belief is that God is Creator, and there it stops. Religion doesn't t go searching for how God created because the purpose of religion is not to explore the physical realm but the best way to live with each other in this realm. If someone want to explore the physical realm further, not a problem, any more than if someone wants to explore new and tasty ways to serve crickets. People of faith believe there is more to life and to living than simply surviving and learning about the physical. We believe there are two realms--the physical and the spiritual.
Bishop Ushher aside, the entirety of the Bible is ultimately translation of tales and fables authored by men largely unknown and written decades / a century and more after the alleged events.
A great many events in the Bible hinge on incidents that simply do not occur in nature. This is easily reconciled if one accepts that (a) Biblical authors engaged in hyperbole, i.e., exaggeration for literary effect, and (b) the stories of supernatural creation, of Noah's Ark, men rising from the dead, etc. etc. are metaphorical.
The typical religionist has a problem with the Bible being a collection of metaphors.