In Bloomburrow Quick Draft, I cast Mind Spiral targeting myself to draw three cards. I also targeted my opponent's creature to tap it (giving them a tapped Fish token).

Then my opponent protected his creature by giving it hexproof in response. The Mind Spiral fizzled.

So how could it get countered, because of illegal targets?
One of the targets (target players draws three cards) is still legal!

In the rules, I read:

…If all its targets, for every instance of the word “target,” are now illegal, the spell or ability doesn’t resolve.

So the hexproof made one of the spells targets illegal, so it should still resolve. Am I right?
Or am I missing something?