To split to columns, with some maximum number of columns, you can try this
macro:

==========================================
Sub SplitToColumns()
Const MaxCols As Long = 256 'set this to whatever or use inputbox
Const Comma As String = ","
Dim c As Range
Dim i As Long
Dim sSplitArray() As String

For Each c In Selection
sSplitArray = Split(c.Value, Comma)

For i = 0 To UBound(sSplitArray)
c(1 + Int(i / MaxCols), 2 + i Mod MaxCols).Value =
Replace(Trim(sSplitArray(i)), vbLf, "")
Next i
Next c
End Sub
=============================================
--ron

I noticed my newsreader wrapped a line in this second macro in the wrong spot.
So as to prevent that, I forced a line break appropriately:

=============================================
Sub SplitToColumns()
Const MaxCols As Long = 3 'set this to whatever or use inputbox
Const Comma As String = ","
Dim c As Range
Dim i As Long
Dim sSplitArray() As String

For Each c In Selection
sSplitArray = Split(c.Value, Comma)

For i = 0 To UBound(sSplitArray)
c(1 + Int(i / MaxCols), 2 + i Mod MaxCols).Value = _
Replace(Trim(sSplitArray(i)), vbLf, "")
Next i
Next c
End Sub
===========================================
--ron