a mathematical structure is an abstract, immutable entity existing outside of space and time

Recall that a mathematical structure is an abstract, immutable entity existing outside of space and time. If history were a movie, the structure would therefore correspond not to a single frame of it but to the entire videotape.

The frog viewpoint who sees randomness all around it

is not isomorphic to the Birds eye view simpliciter, simply 

 simpliciter simply; unconditionally, the Frog's view of reality 

is an unreality, as is the Birds different eye view.  one could argue that our universe is somehow made of stuff perfectly described by a mathematical structure, but which also has other properties that are not described by it, and cannot be described in an abstract baggage-free way.

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