Evidently they were not that avy aware. Having the gear is great, but the knowledge is also equally important.
The number one rule when traveling in avalanche terrain is to expose only one person at a time to dangerous areas. No matter how you slice it, they did not do this.
I see plenty of people who have avalanche gear, but don't have a clue on how to travel properly in avalanche terrain. Likewise, an avalanche doesn't care if you are an expert or not.