Dentsu interview questions

I had a 15-minute recruiter screening phone call which went really well, and the recruiter told me he would progress me to the next (and final) round. He told me to wait for an email from his colleague within the next week to schedule the next interview. I waited, received no email. I followed up three times with no response. A month later, they sent me a rejection email. I was so excited about this role and it was just very disappointing to be treated that way.

contacted by HR first, then 3 rounds of interviews, whereas 2 rounds with team leads, then was told there is going to be a 4th round, where I am supposed to do a presentation. The interviews were friendly and supportive so I believed them. Then 2 weeks gone by not a single response. I emailed the HR expressing my still-there-interest in working with them, but not even a rejection. Whole process is a month now still not knowing what was going on. Utterly disappointed - why is ghosting candidates a trend now with those companies? If not fit then please just reject, not dragging around for 3 rounds (which of course took quite some time for candidates to schedule and prepare) and ignoring the candidates just like that.