I thought it was a clear and obvious error by the referee not to give Spurs a penalty. But the VAR must have decided it was not a clear and obvious error.
This illustrates a fundamental flaw in the VAR process. There is no such thing as a clear and obvious error. It's subjective. The concept of a clear and obvious error is just an excuse to justify a decision.
There is, and I think this case is one that shows that.
If a ref gives a pen and tells VAR he saw a trip, then VAR says there wasn't one, it's a clear and obvious error. The ref gave the decision based on what he thought he saw, but he was wrong. Similarly, ref says he saw ball hit chest instead of arm, but VAR sees it hit the arm, then that's a clear and obvious error. If the ref says he saw it hit an arm, but felt it was too close/natural, then he's given a subjective decision and VAR shouldn't overrule.
With Cancelo and Alexander-Arnold, the ref can make a subjective decision- with Alexander-Arnold he could have said, that he saw the push, but didn't think it was enough for a pen - just one player being strong, or the other going nowhere and waiting for contact. Unless he said there was no push and it was 100% shoulder to shoulder, then VAR wasn't going to intervene. A little like the Haaland goal at Brighton, where it was physical, and could easily have been given as a foul, but once the ref says that he saw what happened and that he thought it was ok, then VAR won't argue.
Clearly (and obviously), we still get decisions where VAR is getting involved when it probably shouldn't, or not getting involved when it should, but the concept shouldn't be difficult. Two refs can see the same incident and make different decisions - Clear and obvious is when the refs reasoning for a decision doesn't match what the pictures say, and that they've genuinely missed something.