Hmmm, I think you're in some in-between-device size size.
The normal smartphone layout already has a mini widget for wikipedia:

But what you're showing is more tablet size I think.
The only way I can reproduce your screenshot is by switching to ipad in my browser emulator.
But even then, it's only in portrait mode that this happens, in landscape mode it has enough space to become a sidebar again


I guess for ipad/tablet sized screens it might be worth considering showing a smaller wikipedia widget yeah. Although it'd have to be something in between mobile 'mini' mode and desktop mode.
Could you send a screenshot of your device's size?
https://whatismyviewport.com/