According to the boss of Red Bull, the gap was too small before they got around the track to the pit entry again, so Lewis would have been in front on tyres that were already warmed up (so an easy defence if Max tried to pass).

Lewis isn't easy to pass, but Max has shown before he can do it... but in this situation it was very debatable if he could have caught up again, so Red Bull were a bit stuck and were just left hoping that Max's tyres would last to the end.