What Mason is doing is making tactical tweaks within Conte's system, and dropping players whose confidence is shot, such as Dier.
He's smart enough to know that he can't fundamentally change formation this late in the season, but he can try to instil a more positive mindset and select players in positions & combinations that emphasise their strengths & provide some protection for their weaknesses.
The right-sided combo of Emerson & Porro is a great example of this, as was dropping Dier & moving Romero into a more central, roaming, position.
At Anfield last week he pushed Sonny up top, playing on the shoulder of the last man and this terrorised Liverpool. It also meant we didn't have to watch our attempts to play out break down because Sonny cannot hold up the ball with his back to goal 10 metres from his own box. Sonny is not & never will be Modric, able to play in tight areas. Give him space to run into and he can be devastating.
My point is that Mason has shown more tactical flexibility in 3 games than Conte showed in an entire season. I'm glad his bold decisions paid off today, even if we were far from perfect.