But if you search the web you will find many photos of self combusting Victrons. All mass produced electronics have an expected percentage of failures, inverters included. The only way to reduce the possibility of failure is to purchase military grade equipment ... and no one will pay that kind of money.
I accept what happened as a one off unusual event, in that the inverter was powered off when it occurred, if you think the same cannot happen to you despite the brand of inverter you own, then you should reconsider. Bit like owners of $2K iPhones exploding in your pocket.