My contention is that it's suspicious because given the references of much more popular projects it takes a long time to raise that amount of money from a wide investing audience.
Well to help ease your suspicions I will tell you why it did as well as it did vs the others you have mentioned. Simply put, both Augur and Lisk were pure pipe dreams with nothing to show but a pretty page saying they would do something with ethereum that had no connection to regulatory bodies or any kind of registered body that was responsible. Instead you put your money in and hope something comes out of it.
DigiX on the other hand was a 1 year old mature project.. had clear plans based on regulatory requirements on how their operation would work, and already had something to show people. It was very clear who the corporate entity that ran it was involved also. Also look at the nature of what they are looking to do.. bridge physical assets with the blockchain. This is of far more importance application wise, and more easily understandable than other said sandbox experiments.
With all that considered, it easily attracts more institutional investors who are willing to throw more money at it. Perhaps not millions, but if they had ethereum as part of their portfolio putting a quarter million into it would just be a good hedge.
So the lessons that should be learned from this is if you want to see that kind of success.. do the hard work first, aim for things that solve real world problems, and don't make offerings pretending to be some mystical decentralized thingamabob that lives outside any reach of being convicted for breaking laws of any sorts. Then the serious money in the world will be able to start looking at your seriously.