People just assume that it's food/light/good water conditions, but there is no proof...
I know one specimen in excellent water conditions, plenty of food and light but the anemone has never splitted. It's HUGE!
Often the bubble tips in the same system split at the same time, and usually there has been a major change in the routine. Waterchange, new bulbs, skimmer failure, temperature swings, even new fishes have triggered the splitting.
Usually they split when they feel like it...