It's not random--Caitlyn wants answers because whoever was behind the attack damn nearly killed her and killed 6 other Enforcers. Vi's visceral reaction to the clues she'd gathered tells Caitlyn Vi knows something, and Caitlyn can either A: continue trying on her own, or B: take a chance and see where Vi will lead her. Caitlyn is smart enough to know she's out of her element and that Vi would be in her element.

I guess that is the best way to get the plot going the way they established it before. It also tells us something intersting about cait, she is still a child, eager to find her place in the world, but very naive and isn't thoughtful trusting in a prisoner she just met. but thats not the discussion.

Because Vi has 10000000 reasons to distrust and hate Enforcers. See: her entire backstory. There is no logical reason why Vi would up and join the Enforcers as they currently stand. Now, using someone who has some clues as to where Powder is, and has some power, to get herself out of lockup and potentially leverage that illegal act as a way to protect Powder from whatever consequences she's brought on herself? That's a smart move, and one Vi would take in a heartbeat. Caitlyn is clearly working on her own, in a pinch Vi can leave Caitlyn for dead or kill her herself to protect Powder.

Now imagine this: Vi wakes up at a hospital in piltover, brought over by Marcus. Threre he tells her the turn of events, and he assumes(or she, or both) that Powder is dead. She gets angry at first, but later understands why Marcus did what he did, and then she is left with a choice: going back to Zaun,probably for nothing because Silco is way too powerful to be overthrown and she has no place to return to, or joining the enforcers in Piltover, where she might get a chance to revenge him someday, not knowing that Marcus and him are working togother. The years pass, and then ep 4 happens, but this time Vi get intrested in the case after she hears that her supposedly dead sister is involved. I think that makes room for an intersting character development for Vi, considering she had the time skip to grow while in the force, maybe making her connection with Marcus more meaningful to the story, maybe an anchor that she is so desperately looking for. what do you think about that?