Well based on my own (limited) experience of recruitment and employers, the first thing I’d do if a recent recruit failed would be to look at the previous short-listed applicants and get back in touch with any I liked. That’s true even if the job has to be re-advertised for bureacratic or legal reasons. In fact given the time it generally takes to get someone in post, I’d say it is quite possible they failed to employ anyone at all first time round.
OTOH, at least the ad presumably doesn’t actually say “previous applicants need not apply” which I have seen in the past…
No harm in applying, but like I said, I wouldn’t get excited.