Syncroness interview questions

This is not so much a condemnation of the actual interviews they conduct, but their communication abilities and capacity for basic courtesy. First was a call from HR, standard base-level interview questions. Got through that and had a video panel interview that was meant to be with 3 people, only 2 show up. Good interview on the easy side. My HR recruiter tells me I made it to the final round of interviews(1 of 3 new graduates) and to stay tuned for an invite... 2 weeks go by without any thing. Finally I got ahold of another HR recruiter and he said he’d be taking over communication. The next and supposedly final interview was onsite in Westminster, CO. I came and met the engineering manager. I had a zoom call in their office with 2 remote workers who were 1st year engineers. They both showed up! Next was a 1 hour written exam that was very expansive from stress strain curves to spacial awareness. I knew all but one question. I then had 2 high level engineers look over my exam and interview me. Range of questions from pretty technical to whiteboarding a project from my resume. Good questions, interesting exchange, I thought I did well. Lastly a 1 on 1 with the engineering manager. He asks me some bigger picture career goal questions and did an exercise on engineering requirements. Cool stuff, very thought provoking. He said they’d get back to me in 2 weeks. Overall great experience in person. Then I wait a few weeks with nothing. Then a different HR woman reaches out and says sorry your previous recruiter quit. She says “It sounds like we could have some exciting news for you and wanted to give you an update on everything”. Weird, ok. I hop on a call and they proceed to tell me they want to bring me on for a project they are bidding that was a good fit for my experience. But they can’t give me the offer until they know whether their bid was selected. They extend me an offer contingent on the contract being awarded. They are willing to give me a signing bonus if I signed it within the week. The signing bonus was measly and not at all compelling. I said I’d love to accept their offer with them as soon as they were ready to honor it fully. I didn’t think that was an unreasonable answer. They ghost me. Haven’t heard from them since. Incredibly unprofessional given the time both parties invested in the process.