^ I think that would certainly have helped, however surely the most likely reason is the total overhaul the Iceland FA completed over the last 15 or so years by building lots of artificial/covered pitches, upskilling its coaches etc...
2018 World Cup qualification (UEFA)
Saw an interesting piece on the BBC about youth drug and alcohol use in Iceland.Maybe another reason for their improvement in football.
In 1998, 42% of Iceland’s 15 and 16 year-olds reported that they had got drunk in the past 30 days. By 2016, though, this figure had fallen to just 5% and drug use and smoking had also sharply declined.
http://www.bbc.co.uk/programmes/p05mw7rd
Fall off in younger drinking in NZ is happening but not that quickly. Hmm...