There is not a specified purpose of the record; the only known information is that, the author wins the game being alone versus 4 computer players, at Hardest difficulty, in Arena-style map.
Beating 4 players is not a piece of cake (especially at the Hardest level), so there seems to be something interesting. After watching the record, though, the summary goes like this: There are no tactics and nothing new,considerable to be presented.
The only difference among any other known ways of playing is the unusual Castle-making rush. You become practically impenetrable that way (already having created many Longbowmen and Cavaliers), but then comes at least one-and-half an hour of boredom with nothing interesting coming up (just seeing the opponents' armies been slaughtered in streams).
The opponents finally have too low resources to manage keeping up, so that's the time to attack!
The fact is, human players are much more smarter than computer players; they would not give it up too easily. Moreover, the game is of Deathmatch type (which is not mentioned in the description).
Your intention of uploading this record might be to show your skills or just show that you are a truly AoE2 gamer. Whatever the case, records been uploaded here have to be entertaining at some point, else there is generally no reason to do so.