[opportune]

I assume the main reason people are using hadoop these days is for HDFS. Spark has supplanted it for actual processing. So the reason hadoop could be so high is that when organizations use part of the hadoop ecosystem (like Cassandra, Hive, and of course Spark) they mention hadoop along with it. Then even though not many organizations are using vanilla hadoop, since it's used in conjunction with many other technologies, it dominates the list.