Caused fire incident that nearly set the entire house on fire

I had a Vizia Mini DC UPS for Wifi 57000mWh which I bought 12 October 2021. In March this year, I noticed the backup supply did not work anymore during load shedding. I opted to buy another one, last Friday 23/05 the new unit blew up leading to a fire incident. Thankfully the fire was contained, would have been a different story. I am still curious on why the unit blew up. The sockets and plugs where it was plugged were still intact and no power tripping happened