How do recruiters/HR actually view job hoppers?

I've heard a lot of people say that job hopping is actually the best way to grow your salary and career because companies often pay more to hire someone than to retain existing employees. I've also heard that company loyalty isn't really rewarded anymore.

But from the recruiter's or hiring manager's perspective, what goes through your mind when you see a resume with several job changes over a relatively short period of time?

Do you see it as someone who's ambitious and looking for better opportunities, or do you worry they'll leave your company in a few months too? At what point does it become a red flag?

For some context, I'm a college student. I recently started working in the IT department at my university library, and I've only been there for about three weeks. It's been a great experience, and they've already trained me for the fall semester. However, I just got an interview for the university's central IT department, which is the position I originally wanted. It has more responsibilities, aligns better with my career goals, and pays more.

If I were to get that job, I'd obviously give proper notice, but I still feel a bit guilty leaving so soon after they've invested time training me.

Would recruiters see a move like this negatively, or is it generally understood that students and early-career professionals take better opportunities when they come up?