Even if it doesn't get enough patronage, it would still continue to run from BXT. Dinhata is a subdivisional HQ and a direct connectivity from this subdivision to Kolkata was decades old demand. As the population of this subdivision is low, so it is obvious that the train train will not get any overwhelming patronage from this subdivision.
And if we go by your population logic, then more than half of the ONT and short distance trains of NE India would have been stopped by now