I would like to ignore you, however you mentioned to me in your post, so I try my best to answer you as reasonably. I ,m just wonder why you again and again spread hatred against Vietnamese ?. You said you are South Vietnamese, but I guess your are Khmer in ethnic, Khmer Krom if I,m right,
I think you are our brother or sister of us, just because we are belong to the people who existed in the world, who shared same native languages, we both are speaking Mon/Khmer languages. In very ancient time Vietnamese/Kinh people and Khmer people we shared same ancestor. Do you know about Sundeland or Sunde shelf ? in very ancient history time from the Late
Pleistocene Age (600,000-12,000 BC), our ancestors were there.
Historians believe that the earliest Vietnamese people (including Mon/Khmer people) gradually moved from the
Indonesian archipelago through the Malay Peninsula and Thailand and up to mainland in China. Then until they Vietnamese/Kinh settled back to North Vietnam the edges of the Red River in the Tonkin Delta.
I know your theory that, Vietnamese/Kinh people never been first in North Vietnam. There was land of Tahi/Katay people. Jiao Zhi people was the Tay/Nung people, not Kinh people. This theory is wrong, bro. Vietnamese/Kinh people not only existed first in North Vietnam, we were also in Laos, in Luang Prabang following your comment.
Last time, I have been to Phnom Penh, I visited the National Museum, I saw the map drawn up the territory of Khmer Empire, it included Laos and Thailand territory. What does it mean ? Vietnamese/Kinh people were there, we were the people of Khmer Empire in gold time, when Laotian people was in China until before 14 Century.
Its great, bro when we could defend our territory of Khmer Empirer and you can rule on us and South East Asia balong to Mon/Khmer speaking people.
Turn back to your question ? why Hoa Lu was first capital of Dai Viet. Its very simple: there is hometown of Dinh Bo Linh. But you have to know that Đinh Bộ Lĩnh ordered hís best friend Lưu Cơ taken a position of Governor od Đại La citadel.
similar question for you: why Angkor wat was the first capital of the
Khmer Empire, not Phnom Penh ?