There are stereotypes, in this case Dhaka Bangladesh women, which are believed and promoted. Those stereotypes never fit an individual. The motivations for finding a foreign bride and for selecting a specific country of origin may follow a common theme but remain unique to the individual.
It may be a man is searching for Dhaka Bangladesh women because “Dhaka Bangladesh women are beautiful”, It may be he is searching because his heritage is Dhaka Bangladesh. It may be because he feels the Dhaka Bangladesh culture produces women of higher moral values, or perhaps looser moral values. Who knows…the stereotype says he is frustrated with the women near his home.
On the other side of the fence the motivations for women to offer themselves to foreign scrutiny are also varied and individual.
I do not think it is right to judge someone for exploring any option they feel might improve their lives. If you believe that true love is rare then it is proper to widen your search to include the entire world. Commitment is also rare and ultimately more valuable. They are not necessarily found bound together in the same relationship.