Publicity. Which they did.
Apart from that, rehashing a beloved old brand is not uncommon. Car manufacturers do it all the time: FIAT 500, Piaggio Vespa, Volkswagen Beetle - they were successfully rebooted after their run had long ended. The commonality was an emphasis on very recognizable designs harking back to their roots. It’s a bit more difficult with the the 3310 because its design is not incredibly different from a million other “candybar” phones, so they targeted its famed reliability instead; a month of standby time is pretty impressive (or at least it is to me, forced to charge an iphone every day multiple times a day). I could see my mom buying this.
