org-export-show-temporary-export-buffer

org-export-show-temporary-export-buffer is a variable defined in `ox.el'.
Its value is

t

Documentation:
Non-nil means show buffer after exporting to temp buffer.
When Org exports to a file, the buffer visiting that file is never
shown, but remains buried. However, when exporting to
a temporary buffer, that buffer is popped up in a second window.
When this variable is nil, the buffer remains buried also in
these cases.

You can customize this variable.