Cricket is equally popular in both countries
But SL has a World Cup to its credit. Was a power even in Test cricket not too long ago
Yet B'desh remain minnows some 2 decades after being given test status
A region where Buddhism was formidable prior to the onset of Islam
Speaks an Indo-Aryan tongue
And much of its people originally hail from what is now Bengal/Orissa
So genetically and culturally there is much that unites Bangladesh and Sri Lanka
Roughly thrice as rich
So Sri Lanka clearly is outperforming in a huge way in many aspects - be it Cricket or the economy
About 10-15% of its population has its origins in the Tamil country in India - large chunks of which practice Hinduism
What I have heard is - at least some decades ago Tamils outperformed Sri Lankans
Not sure if that's still true
Sri Lanka = $12K
TN = About $10K
But an all time Tamil Nadu Cricket team is unlikely to beat an all time Sri Lankan team though SL is barely a third of Tamil Nadu's size in terms of population