Complex sentence: The name was officially capitalized in many different ways, initially being NextStep, then NeXTstep, then NeXTSTEP, and became NEXTSTEP (all capitals) only at the end of its life.
Split into simpler sentences: The name was officially capitalized in many different ways, initially NextStep, then NeXTstep, and also NeXTSTEP. It became NEXTSTEP (all capitals) only at the end of its life.