Wind deflection depends on velocity and BC because it is a percentage of the overall drag on the bullet that is determined by the vector combination of the bullet's headwind with the meteorological wind.
Here's the issue with random luck. Below, I straightened up your image in Photoshop by making the center bull round, and increased the contrast and sharpess a little and put it into the OnTarget TDS program. Then I split it into two groups, for which the stats are in the second image below it.
Note that the above image has stats for both the 4-shot group (upper) and the 3 close shots (lower) as its own group. So here's the trick. Looking at the three shots as a group and considering its radial standard deviation. The software gives 0.103" using the standard formula for sample standard deviation (SD), which doesn't work very well for sample sizes smaller than about 8, so I applied the zye of n method and got an estimate of 0.133". But that's not really important. What is important is that a single flier 3.4 inches away is about 25 standard deviations from the other three. If you assume the three tight shots were truly representative, and if you further assume all four had load components and shooting precision that were identically noisy, the odds against that outlier being purely random are astronomical. To give you some idea how astronomical, Excel runs out of decimal places for calculating that at 7.96 standard deviations, at which point the odds are 562,949,953,421,312:1 against the source of the error being random. So from that perspective, something happened that wasn't just random noise in the shooting system.
If I take the reverse approach and say the upper data represents the true average group size and ask what the odds are of all three out of the four landing in that same spot, I get about 335,000:1. Not so astronomical, but still arguing pretty strongly against the odds of the group's shot distribution being random. Again, this indicates it is far more likely some discreet abnormality occurred, be it the bedding shifting, the sights or their rings shifting, or a bad bullet being responsible.
One other thing that could cause it would be have three perfectly concentrically seated bullets an one that was crooked in the case. Normally, I would expect that to have only about half as much effect as that flier illustrates, but at least it is something that can be inspected for.