It's all about avoiding collaboration. So PoW uses mining to randomise who can publish the next official block/record in the chain. If there were a schedule of which miners would be publishing, in what order, they could collude or be threatened to falsify the data over multiple blocks; causing all sorts of problems.
Because the next block could be mined by anyone; its incredibly hard to co-ordinate fraud or attack the network.
DPoS doesn't use mining like that, it uses trust instead. So our miners (witnesses) are voted into their positions, and publish blocks in a known order. It's stake weighted, so the more HP you have, the more important your vote is.
The community votes for witnesses who have backups, and who hide their identity/location etc. It's generally considered somewhat less safe than PoW, but it's much more environmentally friendly, as computers aren't doing work, just to prove they did work.