A fishing boat crowded with migrants traveling from Libya to Italy sank in Greek waters last week. While hundreds are still missing and feared dead, it has garnered far less attention and resources than the Titan rescue efforts for five people.
Compared to story about yet another ship carrying illegals that deliberately sank, it is not that often that you hear about a "homemade" submarine that disappeared somewhere near the Titanic. And, in this case, it is/was a race against time to try and find the submarine, therefore we see frequent updates in the news.
Understandable that a race against the clock (that I think they've most definitely lost) makes for more novel news, so I'm not surprised that it got more coverage. It's also very fair to be angry that five billionaires on a pleasure trip are visibly more important than 400+ poor. "llegal" people are still people and they suffered and died the same in an effort to live safely, which literally everyone wants.
There's nothing in this article or others I found that suggests it was deliberate, either. It seems to have been an accidental capsize.