SerpApi Senior Engineer interview questions

TL;DR Received an offer, offer later rescinded. From initially reaching out to SerpApi to receiving an offer, the process took around 3.5 months. I interviewed with the CEO and 3 Engineering Directors. One of the interviewers did not show up to our first scheduled interview, and did not respond to emails I sent to confirm date and time. Throughout the process, it took 1-2 weeks after each interview to hear back from the company. After the interviews, one of the Engineering Directors extended an offer for USD $34/hr. The offer was for a contract position, which had not been mentioned at any point prior, and did not include any stock, bonus, health care, holidays, or equipment. The offer did include a profit sharing program, which added USD $200-300 per quarter. According to their calculations (which assumed working 5 days a week, 52 weeks a year, with no vacation), the salary was on par with a Senior Software Engineer salary where I live. The salary was around 40% of what I was getting paid at my previous FAANG company of 7 years. I negotiated up to a rate of USD $65/hr. After some back-and-forth discussing terms in the contract, I let them know I would be home for Christmas holidays, and asked for part of that time off in advance. SerpApi told me they would prefer starting after the holiday season (1.5 months from that point in time) to avoid any breaks during ramp-up. I told them that is fine, and that I would need some time to finalize travel plans and come up with a new start date. 16 days later, I sent an email with a proposed start date. The Engineering Director responded to my email saying they had assumed I was no longer interested in the position. I told them yes, I am still interested in the position. The Engineering Director then told me that my offer is rescinded. Curiously, SerpApi never counter-signed the contract I sent in almost a month prior. The CEO and other employees described SerpApi as an open and transparent company -- even the salary of colleagues was accessible to everyone, they said. I asked for some feedback as to why the offer was rescinded. No response was given.