Marcel knew what he was expecting when he set out on that journey to Draven's residence. He was taking a huge risk here, but it would be worth the effort if he succeeded. While Richardo had not planned to turn him against the Draven family and it happened thanks to his father's foolishness, he knew the bastard was on the sidelines waiting for when to strike after the Draven family was done launching the first blow.
Thus, Marcel could not let that happen. It was hard to see the bigger picture when blinded by the thrill of war, and he had to prove to Eric that it was not worth it to spill unnecessary blood during this period. Sure, Richardo had it out for his family, but they can't forget where he got that kind of power. He zeroed the Basil family to get into that position of power and what was the assurance that he wouldn't come after them next after getting rid of the Luciano family?