Someone was stopped just before the line.
@gnomesayin is correct. The Kawasaki that stopped just before the finish line was #151, Dakota Tedder, who was a lap down to Tomac. He may have been confused or uncertain about his running position relative to Tomac, who is not his teammate but both are Kawasaki riders.
I don't like team orders either, but any long-time observer of motorsports should not be surprised. The net effect is that Dungey can clinch the title with a 4th place in Las Vegas, and without the gift from his teammate, he would have needed 3rd place to clinch. What a dreadful performance by Eli Tomac, but he has had a stellar year, and IMO he deserves the title. That point scale is too flat and under-rewards race winners, but that is a discussion for another day.
I've enjoyed watching SX this year. Hard racing at the front, although the field is woefully thin in quality. It pretty much always has been this way. And the racing has been exciting and real, despite the fact that SX is the most spoofilated, tricked-up-with-gimmicks racing anywhere. I guess Rallycross is as spoofilated, but I've never found that exciting or interesting, YMMV. Also, the Supercross telecasts have been good. They shied away from the team orders question, which was not cool. Should have acknowledged and explained the inevitability of that deal, IMO.
Hoping for an upset in Las Vegas....