He didn't even think he hit anyone, saying "Sorry, I lost it in the straight line", thinking he lost the car and hit the wall purely on his own.
From what I read, Dixon was in fourth gear... I know Indycars have a lot of power and can spin the tyres in lower gears at will (pun not intended), but in fourth? Will Power needs to learn to be a better liar.
Will Power's pit crew casually strolls through his pitbox, dangling a tyre behind him, which hits Dixon's rear tyre as he leaves the pits, knocking Dixon out of a potential victory and into fifteenth (it's worth noting that Power wasn't in his pitbox straight, he was at a slight angle facing the pit wall - making Dixon's exit tighter than normal); then he cuts across the front of Dixon on a restart with 20-ish laps remaining in Baltimore while running in the top six, putting Dixon out of the race and enabling Castroneves - his teammate no less - to extend his championship lead.
Once is accidental, twice is no coincidence.
Call me patriotically biased, but I'm not buying Power's excuses.
Relevant driver quotes:
Scott Dixon
"The No. 15 (Graham Rahal) should have received a penalty (for spinning us) and the No. 4 (Oriol Servia) car passed us on a yellow. So that restart near the end was a complete botch," fumed Dixon. "On the restart I had an overtake advantage on Power, it must have been in fourth gear, so they can't complain about wheelspin. Then I got beside him and he ran me straight into the wall. Then, they wouldn't bring the car back."
Top end of third/somewhere in fourth seems like a high enough speed to not have wheelspin strong enough to pitch a car sideways like that - otherwise how do the drivers keep themselves straight in slower-speed corners or early sections of a straight?
And then there's the race control calls, or lack thereof...
Will Power
"I feel really bad," he declared. "We had a good start to the race in the Verizon car but then I made a mistake on the first pit stop and then the accident on the restart that really ended up ruining two good days. I thought I had a really good run on Bourdais and I was going to the inside to get around him, and I thought I hit a bump or just lost it on cold tires. I really had no idea that Dixon was there. I actually didn't even know until I got back to the pits and they told me. I feel terrible for him and his team. All I can do is tell them how sorry I am and move on to Houston."
Power doesn't even know if he lost it on a bump, lost it due to cold tyres or lost it because of something else. Pretty sure you'd be able to tell if you lost it on a bump large enough to spear your car hard right, and if you're going in a relatively straight line like he was then cold tyres are unlikely to do that either...