Still this paradox is too detached from reality, maybe for its time it was smart. How can we know what is the chance of universe create brain and how many brains there will be per universe? How can we know that universe fluctuation is less likely than brain fluctuation? without this numbers we know nothing.

Universe filled with many brains fluctuation can be more simple than brain fluctuation. Fluctuations may also happen in environment that doesn't even have atoms that are needed for brain , but will have atoms that are needed for universe. Maybe this atoms needed for brain can only be created by universe fluctuation.

If we assume all this unknowns and create our imaginary universe yes there can be more brains in it than universes.