At his peak Sonnen was a beast, and Izzy hasn't show that he has a legit world class ground game like Maia or Silva did.
It's likely that Chael's pace and willingness to grapple sees him clinch with Izzy and get him down at some point, and then it becomes a beatdown. People forget Andy had one of the best defensive guards ever, completely stifling guys like DC and Hendo from doing damage or advancing position. Costa and Whittaker had plenty of moments to clinch izzy, it just wasn't their style and they weren't willing.
Izzy doesn't have the power, chin, clinch game, or speed that Andy had. Chael would be able to walk him down a lot easier. Maybe izzy could survive and find a TKO late but people forget Sonnen has wins over Bisping, Shogun, Stann, Marquardt, and Okami. from 2008-2013(aside from the Rashad fight), the only men to beat Chael were either GOATS of their respective divisions (Silva, Jones), or a GOAT tier MMA grappler (Maia).