Safari documents and data

Have you checked your Reading List - as this will contained saved web pages?

From Safari, tap the “book” icon to the left of the address bar - then tap the “spectacles” icon to reveal your saved (Offline) reading list.

The next logical step to clear any residual cached/temporary data would be to reset and reinstall iPadOS. Before doing so, ensure that you have a current iCloud or iTunes backup from which to restore your data, then:

https://support.apple.com/en-gb/HT201252

This process will erase all data, reset all settings, then reinstall the latest supported version of iPadOS. At the end of the process, you can optionally restore your locally stored data from your backup.

Force-close all Apps. To do so, swipe upwards from the bottom edge of the screen to reveal the Task Switcher, then swipe each App off the top of the screen.

After the Apps are forced-closed, you should force-restart the iPad:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On an iPad with Face ID: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

Just to be clear, have you tried this?

Settings > Safari > Clear History & Website Data