Freight Logistics Solutions interview questions

Interviewed here last Monday for a Logistics Administrator position, Interview went smoothly enough, was low-balled on Salary twice, the salary advertised was 21k, not "up to", but I had to fight to receive an offer of £500 less of what was offered. Was offered the role not 10 minutes later while I was in the car journeying home, FLS wanted me to start the day after but I had some other commitments to finish and another job offer I had to turn down to accept this one, the following Monday was the agreed start date and contracts would be sent out shortly. On Wednesday, 2 whole days after accepting the job and declining the other job offer, I was called to be notified the Business heads had a meeting and decided to rescind my job offer, advising that "Business needs had changed" and they were going in a different direction, despite my start date being 4 days away. Surely this is something decided before posting the job advert and offering the role to someone? Before wasting everyone's time and knowing full well that I had to decline another job to work for FLS? All in all, a very negative experience throughout and I hope they can make processed to not be this flippant in future.