What I've read is that crows are smart for the same reason that dolphins are smart ("social intelligence"). Crows also tend to live in flocks/groups, unlike many other bird species.
Not a great source, but here's an excerpt explaining that they tend to grow up in groups:
But growing up is a different story. During younger years, they often live in larger flocks dubbed juvenile gangs. "It's exactly how it sounds: they're basically a bunch of teenagers trying to compete with each other," Brown says. And it's these relationships they have to keep tabs on.
Not a great source, but here's an excerpt explaining that they tend to grow up in groups:
But growing up is a different story. During younger years, they often live in larger flocks dubbed juvenile gangs. "It's exactly how it sounds: they're basically a bunch of teenagers trying to compete with each other," Brown says. And it's these relationships they have to keep tabs on.
https://cosmosmagazine.com/social-sciences/why-are-crows-so-...