Alright. STRQ Prediction Time.
So, Summer’s dead. And judging by Hazel’s comments in Volume 4, Team Salem probably were the ones that killed her. We also know Summer was the team leader of STRQ, since she’s the first letter in the lineup. So, where am I going with this?
SUMMER WAS BASICALLY THE GLUE HOLDING STRQ TOGETHER/THE BIGGEST THING KEEPING THEIR CHARACTER FLAWS FROM GOING OUT OF CONTROL
No, seriously. Think about it.
So, Summer gets killed by Team Salem on some mission, the details of which aren’t that important, for The IlluminOzi
Taiyang: He shuts down. We know he shuts down because Yang tells us as much all the way back in Volume 2 Chapter 6. He closes himself off from the wider world, teaches at Signal. Could he be doing a lot more than training some kids? Sure. But he has Ruby and Yang. And he doesn’t want to lose them. Or them to lose him. And so he’s stuck on Patch for over a decade. And then when he tries to branch out into fieldwork again, The Fall of Beacon happens and he’s back to caring for Yang and Ruby. (While also trying to keep them in the dark about Raven and the Silver Eyes respectively, based on his reaction to Qrow in the Volume 3 finale, because he wants to keep them safe) And then come the end of Volume 4, he’s still unwilling to leave, despite earlier claiming he’d go after Ruby if he didn’t have to worry about Yang’s wellbeing after The Battle Of Beacon. Although when we see him sitting in his house in the Volume 4 finale, it’s obviously not a decision he makes lightly.
Raven: She doubles down. She’s already quit the team. Left the kingdoms. Left her brother, lover, and daughter behind in order to look after the Tribe. And she’s a Bandit Queen. What do you think her former leader getting killed for Ozpin’s crusade tells her? That she was right. She was right to leave. That she was right that Ozpin will send her and people like her to their deaths if it means keeping the masses safe. So, she fully embraces “The Strong survive. The Weak die.” Adopts the Spring Maiden, and dedicates herself to expanding the Tribe and making it as strong as possible, no matter how many villages she has to bring to their knees to do so.
Qrow: Whether you believe Qrow’s feelings for Summer were romantic or platonic, it’s clear from how he keeps his photo that he took Summer’s death hard. His team photo is tear stained and it has a prominent mug stain over Summer’s part of the portrait, which implies he’s covered it with a glass so he wouldn’t have to look at her. Qrow, already suffering from major issues from growing up in a bandit tribe that knew he was a liability due to his Bad Luck Charm nature and named him as such, likely blames himself. His I’m A Bane To Every Life Complex worsens and the guilt makes him even more loyal to a fault to Ozpin, and even cagier about keeping others in the loop even if it would be beneficial to the cause. Like the whole telling Ruby half the story and using her as bait thing. Or his argumentativeness with Ironwood and Winter. (It also probably either kickstarts his alcoholism or makes it worse)
TL;DR: The surviving members of Team STRQ all lost a friend, teammate, leader, and/or lover and are all handling it poorly.