Here's Why Snape Was Right to Blame James Potter for Lily's Death… Kind of
Severus Snape told Harry that his father was “weak” since he still blamed him for Lily’s death — and actually, he was right. In many ways, it was James’ fault.
There was a ton of hate that James Potter and Severus Snape felt for each other, and they both had a bunch of reasons for it. James despised Snape’s attraction to the Dark Arts and his unkemptness, and Severus hated Potter Sr. for bullying him and being a popular guy despite his behavior. All in all, they were typical high school rivals.
And, of course, they both loved the same woman.
The stakes only rose higher when the First Wizarding War began. Snape was on the Dark Lord’s side, and Potter joined the Order of the Phoenix. Now, they were enemies — but everything changed when Lily’s life was in danger. Without knowing it, both men tried to protect her and her son, but both of them failed.
And honestly, while Severus Snape was too harsh with his words when he called James Potter “weak,” he certainly had a point: there were too many things James messed up that led to his and Lily’s death.
James put his trust in the wrong person. Instead of taking his family’s safety into his own hands and becoming his own Secret Keeper or using the help of the infinitely more powerful Albus Dumbledore for that, James chose literally the weakest and cowardliest wizard he’d ever known. This was his biggest mistake, of course.
However, he also really, really messed up as a wizard.
James knew that his family was hunted by Lord Voldemort, and he knew there was a literal war going on. He and Lily expected no guests on the day Voldemort came to their house, and what did Potter Sr. do? He simply opened the door after hearing someone knocking on it, and not only did he not have his wand in his hand — he also left it in another room!
This alone was a hugely idiotic move on James’ behalf as in both instances, he was too trusting and overly confident to take the threat as seriously as the situation dictated. It’s not like Potter Sr. could’ve deflected the Killing Curse, but if anything, he was supposed to have his weapon in his hand when an uninvited guest came.
So Snape’s accusations hold quite some water if we’re being honest. But look, let’s not forget that it was Severus Snape who doomed the Potters in the first place — so he was much more to blame for his beloved Lily’s death. Snape let her down every step of the way, and blaming her husband, who he hated, was his way to let out his frustration.