Negligence in changing of tires

It's taken me nearly a year to fully process my experience at Vestoration with Tim. In October 2020, my boyfriend needed to service his new Royal Enfield and we had heard that Vestoration specializes in Enfields and Vespas - so while I was there, Tim recommended that I change the tires of my vespa as I still had the original, thinner ones on. I agreed immediately, opting for safety first. When I picked up my vespa a week later, I had an accident 15 minutes after picking up the bike. My back tire burst and I flew off my bike at 60km/h coming over Kloof Nek in busy traffic. After the accident, I received second, third opinions that looked at my bike and all agreed that there was definite negligence in workmanship. The inner tube hadn't been changed (despite having old punctures), there was a mountain of grease on the tube (which I have been told is not good practice) and there was no puncture on the outside tire (indicating that it most likely was a pinched inner tube, which would have occurred during the changing process). Tim seems like a nice guy and I don't believe there is any bad will but poor workmanship, however seemingly minor, can cost you more than just a bike.