Since no one knows what dark matter is, there's no known connection between it and real matter, so 1:5 seems coincidental if it's free to be anything within the

Since no one knows what dark matter is, there's no known connection between it and real matter, so 1:5 seems coincidental if it's free to be anything within the range 0 .. infinity. But there's no reason to think there is or isn't any connection, since nobody knows what it is. Cosmology error bars can be very big, depending on the measurement. 500% difference is certainly bigger than some, but since the vacuum energy density appears to differ by a factor of 10^60 from prediction, it's not necessarily a show stopper. Arguably the biggest discovery in cosmology in the last few decades is how much we do not understand at all.