Like I said, both the characters have their traits and weaknesses. And it's an endless discussion comparing both, especially in a neutral mind. Yes, he was tricked but what was he supposed to do? Find clues about who's responsible?
"But at forest, I saw the footprints. And it matched your boots. IT WAS YOU WHO MADE ME MURDER MY WIFE!"
"NO, YOU LIE! MEDDLING KID!"
Gabriel lost his wife, and the world was coming to an end therefore he wanted to slay the Lords, even if it was for Revenge, he is saving the world at same time. He can't control his fate. No one can, some are lucky to be able to control others' fate, let alone their own. Gabriel wasn't that lucky. And who's saying Gabriel is a brute? The guy is a combat tactician, not an army strategist. Generals and Soldiers are like Ying Yang. They can't live without each other. You may be a king and have your army, but when there's a revolution, that's all brute strength of the people combined together to get to the king. Strategists use their resources to fend for themselves, because they can't do it themselves. You can be a Scrawny Math Nerd who gets dominated by a muscular bully in high school, or you're the Scrawny Math Nerd as a large corporation owner in 20 years who's robbing away the muscular bully's bank dry in vengeance without being detected by the government and their cyber agents because he is an unreal tactician like that. Apples and Oranges. It's different situations. Mathias being a genius man is also the biggest fool in the series, he couldn't accept how life is and wasn't fortunate that he is a rich manor, a royal and an alchemist. According to Castlevania LoI, only handful of people carry this gift and yet... He cursed himself and ruined thousands of life in vain of his wife's death in Span of 1000 years, somewhat not including Lisa. This man wasn't a rational thinker using his best friend and his love's life to gain his power and trying to prove a point to his friend later only after deceiving his friend so he could sympathize with Mathias. This guy was fucked up and needed a psychiatrist for thinking this way. He doesn't even deserve the anger and grief, yet alone become a being of death and wrath for his sad cause. People die, that's that. That's how the world works, and people have being grieving over their loved ones for thousands of years and some take longer than others and curse life because they have to live their life without their family significant others, but Mathias... Wow my boy, his tale is just depressing...
For Gabriel, let's just say there was no forgotten one and Laura was either dead because her master is gone or she was gone and is free forever or whatever after fighting Satan. Gabriel is only left with grief and sadness as he says in the narration minus Laura's voice in Reverie. After what he has been through in span of few days with the death of his childhood friend then his wife, death of an innocent girl and her guardian, death of a spiritual being who sacrificed himself for Gabriel's cause and then find out that his ally betrays him and find out he's responsible for Claudia and Marie's death. You're broken. Gabriel feels there's nothing to really live for. Maybe he would go back to the brotherhood and say "F*** You!" Throw his cross and discard his uniform for good. Would he turn against the world just because of his personal problems? Of course you can't get over his event and his grief and hatred is far stronger than Mathias, and we know Gabriel's character for being a moody, yet strong and kind man with good heart. After this event he probably lost some of those traits, but as his life went on... He would get more softer in his loss and would remember Marie's dying wish and repent for his undeserved sins, unlike Mathias who cursed not only God but disrespected Elizabetha as well. Elizabetha probably would be grieving herself knowing that Mathias has become a monster. Gabriel might find someone else, even though you can never replace your "Childhood friend and then wife", he would have found some nice village girl to keep him happy and get that old feeling of love to give back like he did to Marie. Since I'm subtracting Laura away from this, this means the Brotherhood of Light never had the Prophecy or were wrong about Gabriel being evil later on and then maybe reveal that everything was okay after all and reveal Trevor to Gabriel (There are conflicts in this statement but with Laura gone, some things change as well). Worst case scenario, Gabriel isolates himself and tries to, but fails to get over the events and cannot bare the pain any longer and commits suicide therefore, trapped in Limbo. Gabriel's desire to Curse humanity is highly unlikely.