Foul or no foul?

When is a foul not a foul? When referee doesnt see it! Spurs player barges Leicester one on edge of area ref 10yrds away got a full view doesnt do anything players no appeal to mention.... 2 mins later VAR stops game says it's a penalty Point is if ref doesn't think it's even a foul why did var get involved? It Was a penalty no question so are refs just waited for VAR to make decisions for them or is he incompetent for not blowing up at least for foul?