Just what cultural factors might be expected to be influential? Some ideas are:

• unwillingness of Japanese learners to make mistakes in public / conformity
• 'shyness' (?)
• technological savvy / familiarity
• keeness on games

Potential hypothesis:

Because Japanese language learners are constrained by unwillingness to make mistakes in a 'real' class - because this would mean to 'lose face' and display weakness - interactive and engaging online language learning can provide a valuable tool for language learning.