Why was Maximum Security disqualified in the Kentucky Derby?

Why was Maximum Security disqualified in the Kentucky Derby? 

More than 20 minutes after Saturday's 2019 Kentucky Derby, Churchilll Downs racing stewards disqualified Maximum Security, the first horse across the wire, and named Country House the winner in a controversial decision.

Turning for home, Maximum Security, ridden by Luis Saez, floated out to the right and impeded the chances of several horses including Country House, (1) War of Will, and (18) Long Range Toddy. Country House eventually crossed the wire second behind Maximum Security. 

When a horse comes over on a rival and impedes its chance of winning, stewards can change the placings, either by making their own inquiry into the results or through a jockey or trainer objection. In this case, Flavien Prat, who rode Country House, lodged an objection.

It was the first objection in the Kentucky Derby since 2001, when jockey John Velazquez, aboard second-place Invisible Ink at 55-1, claimed afoul against the winner Monarchos. The claim was disallowed. 

Below is a photo of Maximum Security making contact with (1) War of Will. 

Barbara Borden, chief steward for the state of Kentucky, issued a statement on the behalf of the three stewards, including Butch Becraft, also State of Kentucky Steward, and Tyler Picklesimer, Association Steward. 

BARBARA BORDEN: "The riders of the 18 (Long Range Toddy) and 20 (Country House) horses in the Kentucky Derby lodged objections against the 7 (Maximum Security) horse, the winner, due to interference turning for home, leaving the 1/4 pole.

We had a lengthy review of the race. We interviewed affected riders. We determined that the 7 horse drifted out and impacted the progress of Number 1 (War of Will), in turn, interfering with the 18 and 21 (Bodexpress).  Those horses were all affected, we thought, by the interference.

Therefore, we unanimously determined to disqualify Number 7 and place him behind the 18, the 18 being the lowest-placed horse that he bothered, which is our typical procedure."