Interesting article. This is a good quote, here:
Patrick Barrett banged out the expansion packs using Edith (he had a team of object programmers, number unknown). He was efficient, but he was very proprietary about the use of Edith - he didn't want that to get out, and in effect he established a kind of fiefdom within EA/Maxis. He controlled the development tool, so he controlled the development of the expansion packs. Arguably that policy was reinforced by the scarce resources.
I assume "scarce resources" basically means lack of time (due to EA's infamous deadline idiocy).