Kelpi interview questions

After seeing my resume on career builder they reached out via email and invited me to interview with their HR Director. Questions and answers were solely via Teams messaging for record keeping. They offered me the job verbally that day then sent offer letter next morning. Since I’d never interviewed with or contemplated working for a startup I reached out to the interview with some follow-up questions to make sure I was comfortable signing on. Never heard a word. Followed up a day later via email in case the HR Director had just gotten busy and still no response. I don’t quite understand how you offer somebody a job and then ghost them when they have a few questions.