There is a great way to visualize a Grand Prix which most people have never seen, even though all the teams use it during and after the race: it's called the Race-Trace or Race-History-Chart, depending on which team you're at, and it's a plot of time ahead/behind against lap number. Fig. 1 shows the Race-Trace for the Chinese GP.
Each car/driver is represented by a line, the x-axis is number of laps completed, the y-axis is time ahead/behind an average laptime. So at the left-hand edge is the start, at the right is the chequered flag. The higher a line is, the further ahead that car is; so the winner is the line on top at the right hand side, in this case Hamilton. The sharp downward steps are where a car makes a pit stop and so loses about 23s relative to the cars around it. The time gap between two drivers on track is shown by the vertical distance between those two lines on the chart. Faster cars have steeper lines, slower cars have shallower, or even downward-sloping, lines.
So what can this Race-Trace tell us? Well, we can obviously see that Hamilton was out-front for the whole race thanks to his superior pace from the outset, pulling away from the field in the first 8 laps and then further extending his lead as other cars pitted. We can see that Alonso undercut Vettel by pitting one lap before him in the first round of pit-stops: when Alonso pitted on lap 11 he was behind Vettel, but because his first lap on new tires was quicker than Vettel's lap on older tires he was able to come out ahead of Vettel after Vettel had made his stop one lap later. Vettel is able to hang on to Alonso for only two laps before suffering a serious loss of pace. Compare Vettel's line in the second stint to those of Alonso, Rosberg, and Ricciardo, it's much flatter. You can see that Rosberg catches Vettel on lap 21 and is stuck behind him for a lap before getting past and pulling away rapidly.
We can also see where Ricciardo catches Vettel on lap 23 and gets stuck behind him for 3 laps. This is the point where Vettel was told to let Ricciardo past and replied with his "Tough luck." comment. A zoomed-in section of the Race-Trace shows this more clearly in Fig. 2.
The reason that RedBull must have issued that order is because they could see (maybe from watching the Race-Trace live) that Vettel was having a shocking second stint and that Ricciardo was going much faster and in a close fight with Alonso. Ricciardo did finally get past Vettel and went on to finish only 1.3s behind Alonso. What would have happened if Vettel had done what he was told? Would Ricciardo have been on the podium instead of Alonso? Christian Horner thought not, saying "Arguably he [Ricciardo] would have been a second further up the road", not enough to catch Alonso.
If we suppose that instead of holding up Ricciardo, Vettel had been ordered to let his teammate past before Ricciardo caught him (and he'd obeyed) then we can fill in those three laps with normal, unimpeded lap-times and see from the Race-Trace what would have happened. Fig. 3 shows a hypothetical trace for the case where Ricciardo wasn't impeded by Vettel (green line with purple dots):
As you can see, it looks like he would have caught Alonso. Whether or not he'd have got past him in the last few laps is questionable, but it would have been exciting to watch! It certainly wouldn't have done Vettel any harm to do what he was told, and it could have got his teammate a podium finish.