This is a common misconception like the first in sex search. Google trends do not show absolute search volume; it is simply normalized data. To find absolute search volume (i.e how many searches were made during a particular period) you need to use keyword planner or similar tool. Showing Sri Lanka on the top of Google trends for a particular keyword does not at all mean that we have the highest no of absolute searches. I am sure we would not even be within top 25 countries for this term on no of absolute searches.