Marshall Pucci is the reason Ilsa is a widow, but also, seemingly, a constant source of strength and hope in her struggle against the darker forces of the world. The fact that he was a billionaire, and left her so well supplied materially, doesn't appear to have hurt either.
Assuming his sister Connie can be believed, Marshall had respect as well as love for Ilsa, and saw her as at least his equal. His desire to protect her does not seem to have arisen from any belief in her weakness, but rather the contrary - a conviction that she would never give up if she knew what was happening, and would in all probability be killed in the process. Both of the women paint him as essentially a good man, though Ilsa has a period of understandable doubt, especially when seeing photographs of him with another woman.
Marshall's failure to keep Ilsa in the picture, however, does lead to the life-threatening events that conclude season two - and, sadly, the series.