If a looming general election also played a role and if the Government nominated 2020 as the starting date, this was, nonetheless, a substantial coup.
Subsequent re-election with a sizeable majority would place Mr Brown in a strong position to press the Government to abandon the conditions that accompanied its endorsement and agree to a much earlier start.
Achieving that goal was made all the more possible by the ill-advised nature of those conditions, which stipulated annual rail patronage must be on track to hit 20 million passenger trips before 2020 and that downtown employment must grow by 25 per cent.
Construction of the link should not be predicated on such narrow parameters. It is, most of all, about the shape of the city, congested roads, and creating an essential and efficient transport artery.
If that is achieved, concerns about potential patronage will disappear. Further, it is about cost, especially as Auckland Transport estimates the cost will rise to $3.3 billion if a start is delayed until 2020.
Given that, the focus of debate about the link should be squarely on funding options for the Auckland Council, which will share the cost of the project with the Government. It has long been apparent that agreement on this will not be easy.
Transport Minister Gerry Brownlee has insisted neither tolls, congestion charges nor a regional fuel tax would be used to pay Auckland's share. His stand echoed that of Steven Joyce, his predecessor in that portfolio. Mr Joyce has also argued the cost of the project would leave little for any others in Auckland over the same period.
Such reservations may not have been insurmountable for a mayor at the height of his powers. Mr Brown would have been able to suggest forcibly, and rightly, that Aucklanders showed their backing for the link by re-electing him and should next be able to choose whether they pay their share through road charges or higher rates.
Mr Brown, however, is clearly compromised as much in the eyes of the Government as his own councillors, who will have more say in the development of major policies. Ministers will feel far less inclined to bow to pressure applied by a mayor who no longer has the backing of a substantial number of Aucklanders.
Here, as in other matters, Mr Brown will struggle to drive things forward.