Direct Free Kick - Hearts v Celtic

The referee Craig Thompson blows for a foul. When the game restarted he stood with his hand raised indicating that he had awarded an indirect free kick for dangerous play.

How the Laws define dangerous play:

“… any action that, while trying to play the ball, threatens injury to someone (including the player himself). It is committed with an opponent nearby and prevents the opponent from playing the ball for fear of injury.”

“Playing in a dangerous manner involves no physical contact between the players. If there is physical contact, the action becomes an offence punishable with a direct free kick or penalty kick.”

There clearly was physical contact and so a direct free kick should have been awarded. Craig Thompson with a clear view of the incident decided it was an indirect free kick. Why would he get such a fundamental decision 'wrong?'

Also in this game Hearts players kicked Celtic off the park with little punishment from the referee. Andres Hinkel was subject to a forearm smash from Hearts player David Obua a red card offence which went unpunished. Incident didn't make the BBC highlights, wonder if it will be subject to the mysterious video review panel?