I am posting this to a thread that was posted eighteen months ago, but that might be interesting to revisit in the current context. As I understand the international rule, Maximum Security would not have come down unless the foul affected a horse (according to the stewards, Long Range Toddy and/or Bodexpress in this case) that would have finished ahead of him. The most common rule in the US requires only that the foul must have cost the fouled horse a placing. The Thoroughbred Idea Foundation are pushing for adoption of the international rule:

https://racingthinktank.com/reports/tif-reports-changing-rules

I like the idea of having more things decided on the track and fewer decided in the stewards' booth. There are ways other than disqualification to deal with fouls.

Disclosure: I lost an inconsequential amount of money because of the DQ, but tend to agree that, under the current rules, it was the correct call.