You're probably between 170-200 pounds stepping on an animal that weighs about 3 pounds on average. As far as it's concerned, you tried to kill it for "no reason". Taking it as some pre-meditated personal unprovoked attack on you is odd.
Yes, I stepped on it...but it's has all the senses to know I'm getting too close... hear, feel, see, heat sensors.
They know when a mouse, bird, or squirrel, is running around on the ground. ...but it never rattled, nor did it zip back under the rocks, before I put my foot down...neither I nor the snake knew where that foot would land, on the next step...but I'd be very close, with no way for it to miss a strike, which can happen, but rare.
(I witnessed one missed my dad's foot as we were walking, it was concealed in the brush, it never rattled either.)
But I was already in striking distance the last step before, and it didn't rattle, which means it was in predator mode, laying in ambush, ready to kill.
They are stealthily ambush hunters, and concealed well in their environments...they own the area they live in.
And one does not go around stepping on rattlesnakes just to be mean to the animals...on purpose. They will kill you.
I have zero sympathy for snakes, I violently kill everyone I see, with extreme prejudice, by any means available...to exterminate them from my area on this earth.
Once bitten...is more than enough.
Do not trust a dead rattlesnake, to be completely dead, control the head, unless severed from the body.