If someone is friendly with you for months, years, and then suddenly becomes cold, that's not because you're an asshole - it's because of some incident that either they witnessed, or was gossiped to them.
When everyone around you reacts this way almost at once, you know for sure that it was gossip.
If I'd spoken to this person along the lines of "OMG WTF are you saying dude that's so stupid" rather than "Actually I think person X had a good point about trying this approach - it would solve X and Y and Z all at once", I'd be inclined to believe that it was just me.
Person X was actually the CTO, so I thought it was a safe topic, but I'd misunderstood the shadow power structure. It turned out the guy I was speaking to had more power (at least over me anyway), and was opposed to the CTO.
Obviously I have no idea the circumstances of your experiences here, so don't take this personally, this is hypothetical: but what if "you" actually were the asshole here? Wouldn't you be saying the same thing? Maybe this incident made people realize that "you" weren't a good person to work with?
If you were on the other side, isn't that a good outcome?