I think the problem with epic historical montage is that it would be expensive for the screen time. Multiple scenes, some with significant CGI might have been cost prohibitive for the first season. I mean you would have to depict the bore, some battles where cities were destroyed, the sealing, some of the breaking, and the actual creation of dragonmount. That is a lot of things for 5 minutes of screen time.
I mean if they tried to go cheap it would turn off a lot of people. I just think it would have been too expensive.