I am sorry but TAP lost the most relevant Portuguese airport in terms of population, so in the north of Portugal we say TAL, just for Lisbon. In old times, probably the consideration for the most important Portuguese region was most more rational, in terms of management decision making.
There are some rumors that the reason is that the base in Lisbon is captured by the pilots that live in Lisbon and do not wish to have other bases, mainly for intercontinental connections.
Just a rumor, but the fact is that this company just lost the 5 millions hab from the north to low cost companies...
:-(