Why was homoousios not mentioned for 20 years after Nicaea?

In the “centuries-old account of the Council of Nicaea: … The whole power of the mysterious dogma is at once established by the one word homoousios … with one pronouncement the Church identified a term (homoousios) that secured its … beliefs against heresy. ... Such older accounts are deeply mistaken ” (LA, 11) “What is conventionally regarded as the key-word in the Creed homoousion, falls completely out of the controversy very shortly after the Council of Nicaea and is not heard of for over twenty years.” (Hanson Lecture ) “For nearly twenty years after Nicaea nobody mentions homoousios, not even Athanasius. This may be because it was much less significant than either later historians of the ancient Church or modern scholars thought that it was.” (RH, 170) “During the years 326–50 the term homoousios is rarely if ever mentioned.” (LA, 431) “After Nicaea homoousios is not mentioned again in truly contemporary sources for two decades. … It was not seen as that useful or important.” (LA, 96) “During the years 325–42 neither Arius nor the particular technical terminology used at Nicaea were at the heart of theological controversy.” (LA, 100) The word homoousios appears only once in Athanasius’ the Orations. This is understood as “evidence of Athanasius’ lack of commitment to Nicaea's terminology at this stage of his career.” (LA, 115) “Athanasius' decision to make Nicaea and homoousios central to his theology has its origins in the shifting climate of the 350s and the structure of emerging Homoian theology.” (LA, 144) > LA = Lewis Ayres Nicaea and its legacy, 2004 Ayres is a Professor of > Catholic and Historical Theology at Durham University in the United > Kingdom. > > RH = Bishop R.P.C. Hanson The Search for the Christian Doctrine of God > – The Arian Controversy 318-381, 1987 Question: Why was the term homoousios not part of the controversy during the 25 years from 325-350 and when and why did this change, so that it is today regarded as the key term in the Nicene Creed?