I see nothing wrong with the move. Kvyat spotted and went for the massive gap inside Vettel who over reacted. Raikonnen then made matters worse by forcing his way back on track in a pretty unsafe way, causing one of the Saubers to swerve in front of other traffic.
If anything I'd argue that people with Vettel's and Raikonnen's experience should know better.
Yes, I'm getting pretty angry with experienced drivers who manage to assume another car won't be on the inside or outside, especially in the first corner.
Massa, Kimi, they seem to regularly get into crap that is entirely their own doing and never learn from it. Kimi swiping bottas in Mexico, Massa cutting in on Magnussen then flipping himself over, Kimi this weekend, they all made stupid assumptions about where other cars where and drove as if they could pick and chose their favourite line as no other cars would stop it.
Kvyat was going wide, there is a good set of images of Kvyat's position around the corner, he swung out wide as natural but at his widest there was well more than one cars width on the outside.
There is no law that Kvyat has to hug the inside and not push Vettel wider, Vettel would have gone wider anyway. In general I would say for most corners the guy on the inside will swing out wide, that is how physics work, you go outside to apex to outside. Diving up the inside as long as you aren't out of control and cause direct contact(Bottas in Bahrain) is fine. Before the contact Kvyat was in control, not locked up and alongside Vettel and they could both have gone wider (as Kvyat did) and gone through the corner fine.
You know a car will drift outside so it's relatively safe to go up the inside in that situation but when you know cars inside you will drift outside, turning into those cars is nuts but that is precisely what Kimi did.
Kimi screwed up, got aggressive on how he thought he'd go after Vettel and assumed no one was on his inside.
The outside is the danger area, inside less so, Kvyat was utterly fine.. had he arrived out of control that is an entirely different matter but he didn't.
The default into the first corner should be assume there are other cars competing and be more sensible in your positioning, Kimi's actions presumed a car wasn't inside vettel and his actions caused multiple collisions for which I think he should have been penalised. Ruined Hamilton's race yet still beat him thanks to the damage caused to Hamilton's car.