At worst those symptoms could be indicative of a partially failed flash memory but let's assume it's a software rather than hardware problem until it's clear one way or the other.

'Soft-bricked' re-booting devices are hard to flash because there's a struggle with the program trying to initiate a flash during the short time it's in preboot before it starts loading again. Once a flash initiates properly the device should hold preboot to allow it to finish. You've been persistent in loading cure fw which is the key to success in such a case.

Although the reformat adds complexity I do fully understand why you did it in this case when you were unable to successfully delete any file manually.

Programs like Updater and G7ToWin use only preboot mode which you'd now have to manually enter preboot to access. Conversely, Garmin Express doesn't recognize preboot - only Mass Storage Mode is useful to it which is why it can now 'see' the dezl with Cure fw loaded on it. Those folders you mentioned as now present would have been added by GE after the initial connection to it post-formatting. It may be something about the dezl GE doesn't like in its present state - the Garmin servers may be suspecting it's not a real Garmin device and not allowing it to be added.

IMPORTANT: How did you reformat it? If you used anything other than RMPrepUSB then do it again using the recommended settings here: [Only registered and activated users can see links. ]. Other tools including the built-in Windows one might not give properly acceptable results in Garmin devices.

Look in this thread for different methods of entering preboot in case there's a screen hold position that works for you there: [Only registered and activated users can see links. ]. Some devices are related hardware (some nuvi models are like dezl and zumo devices around the same vintage for example). Look at Post #92 there for an alternate method to enter preboot too. You will have to enter preboot to flash original firmware once you get the file system properly restored.