Definitely looks like a fix for me. Huge market swing before the match from Trungelliti being 3.0 or more to about 1.3 indicates a ton of money coming in on him.
Also, I suspect that 1st game in the second set may have been a 'spot fix'. If whoever was in the crowd with Milojevic was in on it, once he went up 40-0 he could have given him a sign that he had bet on Trungelliti to win the game. It would usually pay about 20-1 to 40-1 for him to win the game at that point, so even betting $100 would next what is usually a max in-play return of 2k. With a few accounts, they could add an additional 10k in profit on one game alone.
I know of one instance of spot fixing in-play before, where an Italian player was getting up 30-0 and then tanking matches to raise the odds.
The fact that like 80% of the points he lost were either into the net or wide make it really seem like a fix to me, combined with the other information.