Sometimes you'll see this in an interior:
A mirror placed on top of another mirror.
I know exactly what my husband, the engineer (Mr. Practical), would say if he saw this...

”Why?”
Because he’s not one for doing something purely for the sake of beauty or aesthetics - it has to serve a purpose. And if he’s going to spend money, it better be a BIG purpose. :-/
I, on the other hand, would do anything for the beauty of it, for the visual treat it would bring me.
I’m thinking that’s the case here: when a smaller framed-mirror is mounted on top of a mirror that’s been applied to the wall, or even one framed-mirror on top of another.
If there’s already a mirrored surface, then you might want to bring a bit more punctuation to that wall. You might want to draw attention to it a bit more, or add a little more sparkle.
Sunbursts are nice to use here as the top mirror to eliminate a repetition of shape and to highlight their beautiful finish and frame.
Or perhaps you just have a lot of mirrors?
Whatever the reason... I love it.