Booz Allen Hamilton interview questions

Contacted by initial recruiter for a position, but they didn't get the contract for it. A week or two later I was contacted by another recruiter for another position. I had a video interview with three different people. Recruiter followed up after first interview. She was very communicative and informative. The other two interviews were the following week. I didn't receive any follow up until I contacted the interviewers directly the next week who told me they would be making a decision soon. I received an offer later that day. They did a background check which came back clear, and I received an offer letter later that week and a start date for two weeks after. The onboarding process was going smoothly, so I commend them for that. I submitted my resignation. A week after my resignation I received an email on Friday that they would be extending my background investigation because of a discrepancy. There was no follow up until the Monday morning, which was very upsetting. They forwarded my information to the decision committee which was meeting the next week. I received a letter stating they rescinded my offer that day. I understand why it was done, I just didn't like the lack of communication during the process, and now I'm in the unfortunate position of being unemployed.