Why did t Jaehaerys I…(Spoilers: Published)

Build a second, Crown run, Twins?

Jae was very into roads, laws, into knitting the seven kingdoms into one political body - and into connecting them physically via the King’s Road.

It could not have escaped his notice that a minor family were running what we’d call an extortion racket slightly north, and accruing localized power and immense wealth as a result.

This sows emnity within his Kingdom; but also undermines his chosen Vassals, the Tullys, as Liege-Lords of that region;

It also chokes trade and other commerce; and cuts off travel, leaving it at the mercy of one minor family

Why not then, not embark on building a secondary Twins? Either more north or more south, run by the Crown, diminishing the Freys but also giving the Crown an income distinct and separate from taxes?