I have been lucky enough to have been upvoted by both these two whales in the past (I don't know them so I am very grateful for their votes.) and I have noticed recently that Snowflake's SP has dropped to the floor.

I know some people have actually invested their own cash into Steemit, though I don't know if it includes these two whales. For those who have, it's perfectly reasonable to look for the highest return via whatever means available, and they don't have any 'obligation' to vote for anyone no matter how much they like their posts. I have seen some friends with high SP vote 100% for me but the amount is really low as they have delegated a lot of it out. As harsh as it may sound, sadly that's the reality of this platform which drives people's behaviour.