Agreed. I wouldn't put it past them to start fake news but this ain't the tea they'd brew.
I never believe anything without receipts, so as far as I'm concerned this is all currently hearsay and speculation, but highly believable hearsay and speculation. I wouldn't be even the tiniest bit surprised. He's just the type, and while we obviously think he's revolting, it's definitely not unfathomable to think someone much younger, naive and impressionable could be wooed. If you had no idea what he's really like and he laid it on thick, with a good enough sob story about how trapped he feels in his marriage, it could even feel like a romantic little rescue mission. Or just illicit and therefore exciting. Not everybody operates by the same moral code. There are plenty of single people in the world happy to do whatever with whoever - it's on the attached person to be faithful.
It would certainly make sense with his long retreat from social media, possibly realising what a two-faced rat he was being, then coming back on strong when that raised suspicion and had people asking questions. "tit, better stick to usual programming, too much attention otherwise..." He might even have wanted to distance himself online from Sez and family life so it was less of a thing if and when it dropped.
The random reference to their clouds being synced and subsequent clearly-been-crying photos seem damning enough on their own. Plus all the time away recently; rarely sharing anything together and it seeming forced when they do ... additional OTT word salads from Brad ... and even more expensive family activities than usual recently, possibly as neutral ground to have "family time" where there's no choice but to stay civil (and really not have to speak a lot at all)?