https://daphnecaruanagalizia.com/
She was hated by many, both because she was very biased (think more Breitbart than Fox News) and also because she had no reservations about punching below the belt. It is hard to write this without sounding biased, but I never thought of her as a good person nor as a good journalist.
The perpetrator could be anyone, but personally I do not think it was politically motivated since she supported a faction of the opposition that is currently, completely in shambles and she was therefore no threat to anyone. Moreover, most of the Maltese population did not respect her as a journalist because of her overt bias. All the people jumping to conclusions are just doing a disservice to her by possibly misleading the investigations.
There is also no reason to believe that she was killed by some "international bankers" or some such conspiracy theories. Her "investigative journalism" was limited to attacking the PL, one of our two main political parties. She never really ventured past that.
I will not speculate further.