Why do top season crusaders on 4-person team leaderboards have dexterity and intelligence items?

In the Greater Rifts that top leader board players are running, every enemy will kill you very very quickly. To counter this, they dedicate 1 player out of 4 to crowd controlling the enemy by stunning, freezing, fearing etc. This Player will forgo the ability to cause damage in the attempt to prevent their team mates from taking damage.

The builds that you are seeing are known as Zero Damage Per Second or ZDPS for short.

If you were to look at the Crusader solo Greater Rift leader boards you would see very different set ups. This is the number 1 Crusader on the 4 player leader boards and this is the number 1 Crusader on the solo leader boards, notice that the 4 player Crusader has 3194 strength and 2768 dexterity whereas the solo Crusader has 13760 strength and only 77 dexterity.

This is because 100% of your dexterity and strength is added to your Armor with every 10 points of intelligence adding 1 point to All Resistance.

Since they are not doing any damage, their main stat (strength) is interchangeable with dexterity as it provides the same bonus. This means that the priority for an item is how well rolled the other attributes such as cooldown and resource reduction are and not on the type of main stat it has. Also since they will usually be in a group with high dps classes that have dexterity as their main stat (Demon Hunters, monks) there is a higher chance for an item to drop with dexterity.

Their role is to keep the others alive, this is why they prioritise these stats.