There are at least three relevant differences:

1. digg was closed source, steem & steemit are open source. Thus, algorithms like digg's flagging algorithm cannot be secret here.
2. Anyone can invest their way to the top with steem. Digg's insiders were a closed group.
3. Digg's data was hidden, steem's is public - on the blockchain.

As they say, sunlight is the best disinfectant. It's only a matter of time until someone takes advantage of steem's open nature to publish and visualize cliques, quasi-cliques, and other characteristics of the steem voting graph. That sort of openness is not available in a closed environment like digg, and it will eventually limit abusive voting.

People need to start thinking of this platform in terms of months, years, and decades instead of perpetually panicking over the drama of the day. It's not even a year old yet.

Update:
(4) Steemit's users are also investors, which gives them incentive to stick around and fix things instead of jumping ship to another platform (at least for as long as no other platform is doing the same thing). Digg's users were not financially invested in their platform.