The average broadband user has at the least, 10Mbps/UP. If your smart appliances all started sending at least 10mbps up... you only need a million smart TV's to start causing damage.
I'm guessing there's 100M Smart TV's in the USA? Each sending 10Mb/s up? There's 1GB/s of traffic. Multiply this by the next 50 nations who have smart TVs and bandwidth to spare...
Then make it multiuple devices in a home. Then make it every smart device on the planet, using SOME bandwidth... it gets painful fast, and its free for the attackers, since the poor sap with a hacked smart TV is doing the work.