#2 The dominance of Juventus and Portugal
Juventus have an unprecedented stranglehold on the Serie A. The Bianconeri are so far ahead of the rest of the competition that almost every match is a walkover for them in the league.
Also, Portugal's status as one of the elite footballing teams on the European continent ensures that they get relatively easy fixtures during the qualification stages for the World Cup and Euro.
There are over 10 minnows in Europe who are regularly walloped by the top teams, and Portugal get at least two of those when draws for qualifiers are made. Such fixtures offer Ronaldo the chance to bolster his already-incredible goal tally.
Furthermore, while Juventus might not exactly be renowned for their goalscoring prowess, their status as Italian superpowers means that they net a respectable amount every season. And with Ronaldo serving as their go-to man in front of goal, it is highly likely that he will record 25+ seasons for the next few years.