Dear respected Howell Z,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, firstly may I know are you want to change view type in a single list or all List event new created SharePoint list as well? based on my different test I change the view for single List via if you select the compact list view type and then again click on Switch view options dropdown at the top right corner and click on "Save view as" >under save as dialog box select "Save", then when you refresh the SharePoint list page or open it again it will keep the compact list view type.
Note: Just be sure to save the view with the name of the view you're trying to replace. I applied the Compact View and used "All Items" as the name of the view to save it as.
Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution.
I'm sorry and I apologize for that.
Appreciate your patience and understanding and thank you for your time and cooperation.
Sincerely,
Waqas Muhammad