Battery Consumption too high
My question is simple, how and why do I have these problems? Could they be caused by a widget?

It can be caused by anything including (a) widget(s).
However, in this case, it's an issue with iOS 14.

Apple Confirms iOS 14 Battery, Data Problems For iPhone Users
iOS 14 Battery Life Bad &amp; Draining Fast? Here’s Why &amp; How to Fix It

I have personally tested this after experiencing severe battery drain on my iPhone after upgrading to iOS 14.1 by reverting to iOS 13 via a restore from backup.  When I did, the issue went away.
What can you do to fix?  There are some tips like ensuring your apps are updated and closing apps (not suspending them) when not in use.  I personally just keep the phone plugged in all the time and I'm waiting for a new release that hopefully fixes it (actually, I'm waiting for the iPhone 12 mini instead).