Split Data in one cell into below rows

[snb]

Sub snb()
    sn = Cells(1).CurrentRegion
    For j = 2 To UBound(sn)
        c01 = c01 & Replace(sn(j, 1) & vbLf, vbLf, "_" & sn(j, 2) & vbLf)
    Next
    sn = Split(c01, vbLf)
    Cells(2, 5).Resize(UBound(sn) + 1) = Application.Transpose(sn)
End Sub

NB. Avoid merged cells in combination with VBA.