How come CHT falls under the bangladesh region when it was formerly a part of the tripuri kingdom even chakmas were a part of tripuri kingdom. Like how did CHT even came under bangladesh? Did the tripuri king abandoned and gave up his authority on chakmas and CHT?

How come CHT falls under the bangladesh region when it was formerly a part of the tripuri kingdom even chakmas were a part of tripuri kingdom. Like how did CHT even came under bangladesh? Did the tripuri king abandoned and gave up his authority on chakmas and CHT?