Well it's not just you [1]. I don't have any data to support it, but I'm personally guessing either it's a ridiculously massive update, some overzealous ACR, or they may have setup some kind of p2p streaming system for who knows what reason. If you don't want to turn off wi-fi to the TV entirely, maybe try disabling ACR [2] to see if that does anything.

[1] https://www.reddit.com/r/VizioTV/comments/96gtti/vizio_tv_us...

[2] https://www.consumerreports.org/privacy/how-to-turn-off-smar...