Can no longer clear Outlook calendar

-- I used to be able to clear my old calendar on old outlook by switching to list view
-- selecting everything with ctrl A and then deleting.

There is no ability to "bulk delete" Calendar events in New Outlook.

-- I see a calendar in the New Outlook that I don't see in Outlook classic
-- (for the exact same account at outlook.com). It's just all fouled up.

In New Outlook an account can have multiple Calendars in addition to the "Default/Main" Calendar.

https://support.microsoft.com/en-us/office/create-additional-calendars-4b5570c4-e95d-4673-b38a-2b8ead5f00ee

https://support.microsoft.com/en-us/office/delete-a-calendar-in-outlook-9ba1364c-bdb0-41be-8f66-eaf96698d021

You might want to look at the possible ways you can Share, Publish, Subscribe, and Import Calendars in New Outlook.

https://support.microsoft.com/en-us/office/share-an-outlook-calendar-as-view-only-with-others-353ed2c1-3ec5-449d-8c73-6931a0adab88

You might be better served by posting this question in the Outlook Q&A Forum:

https://learn.microsoft.com/en-us/answers/tags/778/office-outlook

This presents your question to a much larger audience and gets you access to the Outlook Subject Matter Support Specialist who monitor that forum.