Can someone explain what happened?

Interned for a company a few years back before finishing undergrad. Now in grad school and looking for jobs. I applied to a senior level position just for fun, then got a call about a week later asking me to come in and do a panel interview with the team. I get there an everyone is nice, but very unprepared/quiet. They didn't ask many questions, sort of just talked. It seems like they hadn't really read over my resume beforehand as they were asking some basic questions that were answered. The second group said that they are interviewing other more experienced candidates and wanted to know what my interests were. Why would they call me in for a 2+ hour panel interview if they were so uninterested/unprepared?

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