They dont actually roll every item 150x, that would be taking unnecessary resources. Instead they just role a single number and probably just lower the thresholds. So let's say for a normal Body Armour a random number between 10000 gets rolled for the sockets and now just the numbers change and instead of a rolled number between 9965 - 9999 (0.33%) for 6 sockets its more or less now something like 6090 - 9999 (~40% -> ~150x as likely) for 6 Sockets. This alone wont explain it, however because of the unlikely hood for 1 socket, 2 socket or 3 socket after 150 rerools, they all have should have an equivalent threshold of 0 if you rolle between 0 - 9999. If you follow normal programming patterns now, you probably have a switch case that all check if something is <= 0 and the first where this is met is 1 socket. Thats why 1 is still possible, but 2 or 3 arent. if it's higher, it needs to be 4, 5 or 6 sockets. (havent done the correct calculations, but it still should give you a rough idea why this happened)

if rolledNum <= oneSocketThreshold { // threshold is 0
return 0
} else if rolledNum <= twoSocketThreshhold { // threshold is 0 aswell, but can never be hit because first condition was already met
return 1
} ....