Because the Commonwealth is so big and cricket has a huge tradition in these countries. Just look at India; they have a population of around 1.34bln (17.5% of the world population) and if I am not mistaken, Cricket is the favourite sport there - one of the few countries, where soccer isn't #1.

Check table tennis sitting at #6. This is mainly because chinese people are crazy about table tennis and they even have slightly higher numbers population-wise than India.

Same goes for Field Hockey, which then again is a big deal in India and quite popular in a lot of other countries (Pakistan, a lot of western Europe countries).