Hi @Mark_Stewart
I have tried the same previously and both Excel Online and Desktop client open up my CSV in columns. In the old days you had to use "Convert Text to Columns" and choose a comma as a delimiter, this should solve your problem short term.

However, why doesn't it delimit automatically? Have you tried creating a csv in notepad and uploading it to sharepoint to see if the same happens? This would confirm if it was your flow or your configuration of Excel.
Once we know what is causing the problem, we can concentrate on exploring that area.
Thanks
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.
Cheers,
Damien