The reigning world champion ran third for the first 14 tours of the 25-lap rain-hit grand prix at Rio Hondo, before passing Alex Marquez for second on lap 15.
Bagnaia looked comfortable in second and nailed on for a podium before he slid off his factory Ducati at the penultimate corner on lap 17.
He re-joined the grand prix and took the chequered flag down in 16th, and has been dethroned from the lead of the championship by race winner Marco Bezzecchi.
Bagnaia says he doesn’t understand why he crashed as he did nothing different at Turn 13 compared to previous laps and is “angry” because he hoped that he’d eradicated these errors from 2022.
“I crashed. I’m very upset, sincerely,” Bagnaia began.
“This is the kind of crash that I don’t understand. Sometimes you crash and you don’t know why, and it’s the most difficult to learn from.
“I did 16 laps, in 16 laps I did the same manoeuvre [at that corner], but on this lap [17] I crashed and it’s also not a normal crash, because normally when you crash you lose the front or you release the brakes too early.
“Today I lost the front touching the gas, so it’s something more difficult to understand.
“But that’s it, I did a mistake. I was wondering if this year I was a better rider, more precise, without mistakes, doing better things.
“And in the second race of the year I crashed. So, it’s something that makes me very angry.”
Bagnaia added: “I was feeling great. Without forcing, without doing crazy things I was second.
“I was already sure that Marco in front was too fast for me, was already with five seconds of gap. I was already there, just controlling the rear with Alex and that’s it.
“So, it’s for that reason why I’m upset. Normally when you are in control you don’t crash like this. So, this is something I need to understand.”
A number of riders said after the race they suffered with tyre wear, but Bagnaia says there was no major drop in grip for him and doesn’t think this had anything to do with the crash.
“I didn’t feel a big drop, because I was so conservative at the start,” he explained.
“I was seeing that Alex in front of me was pushing more. I was so conservative and knowing that after half race I was able to regain the gap.
“And then I crashed the same, because the rear grip on my bike was fine. I was accelerating well, and also the front I was feeling great with it.
“I was forcing the braking a bit and everything was under control. So, it’s for this reason that I don’t understand.
“We know that we were on the limit because the lap times were very competitive, and maybe it was for that reason. But the only thing is for the crash it’s because I made a mistake.”
