I don't know whether the ref went to look at the monitor but if he didn't then he only saw it once and at full speed. I might not blame him if that was the case.
At which point though, VAR with their camera angles, stop start, slow down speed up replays should've denied it. It's plain to see...
There is no justification for giving that penalty.
The VAR bods should be investigated and questioned re their interpretation of the laws and justification for the decision they reached.
If you stuck to the law you would never give that as a penalty so there must be some other reason. Either...