The official timeline present in Daizenshuu 7 makes it apparent he started his attack as soon as he was formed. Kami not picking up knowledge of the Mafuba until his resurgence also supports this when it suggests things occurred too quickly for him to view for long or that it was before he gained the ability to view events clearly from his palace. This is further supported by anime flashbacks.
Roshi recognising Daimao isn't surprising as, regardless of having aged, a big green creature with the same facial structure, clothing and the Ma kanji showing clearly on their shirt is a dead giveaway.