It was was the third world title of Rio 2016 Olympic champion Snyder's illustrious career, but for Japan's Rei it signified a giant step forward in his return from the wrestling wilderness.
Meanwhile, in 20-year-old Iranian Amouzadkhali we may have witnessed the birth of a new superstar.
Snyder's win secured the USA's place atop the overall men's freestyle rankings in Belgrade with four golds, four silvers, and a total score of 188.
A superb final day for Iran saw the Asian powerhouse run them close on 150 points from two gold, three silver, and two bronze medals.
Kyle Snyder wins third world crown
A controlled display from Rio 2016 Olympic champion Kyle Snyder saw him secure a 6-0 win over Batyrbek Tsakulov in the 97kg final.
The Slovakian has been in great form this year with notable Grand Prix wins in Rome and Almaty, but had no answer in Belgrade to his opponent's heavy hands and lightning-fast leg strikes.
Despite looking the fresher of the pair in the second round, Tsakulov could do little to break down the American's rock-solid defence.
European champion Magomedkhan Magomedov sealed a memorable come-from-behind victory to win the first 97kg bronze medal match by fall.
The Azerbaijani went down early to Mohammadhossein Mohammadian, but after several blood stoppages for the Iranian, Magomedov was able to claw his way back into the match before winning it with a superb flip.
The second bronze match in the division was won in dramatic fashion by Georgia's Givi Matcharashvili, who was down 2-0 for most of the match before securing the tie at the death with a chest lock on Vladislav Baitsaev of Hungary worth 4 points to seal a 5-3 win.
Japanese veteran Higuchi Rei wins 61kg crown
Higuchi Rei landed Japan's second men's freestyle title in Belgrade with a dominant tech fall 10-0 win over over Reza Atri of Iran in the 61kg final, that ended before the end of the first round.
The Japanese suffocated his opponent with a variety of ground attacks, closing the space at every opportunity.
It has been a long road back to form for Rio 2016 silver medallist Rei, who fell off his national team's radar before bouncing back to win this year's Asian Championships, and now his first world championship.
The first bronze medal match at 61kg was won by reigning European champion Arsen Harutyunyan.
USA's Seth Gross had no answer to the Armenian's typically aggressive game, who went 3-0 in under 20 seconds before closing out a comfortable 12-0 win.
The second bronze went to Mongolian veteran Narankhuu Narmandakh who eased to a 9-0 win over Georgi Vangelov of Bulgaria.
Rahman Amouzadkhali wins first wrestling world title
Rahman Amouzadkhali of Iran displayed a never-say-die attitude to beat John Diakomihalis 13-8 in a breathless but brilliant 65kg final.
An early flurry of ground attacks from both men and a subsequent successful USA challenge resulted in a scoreline of 8-6 for their man.
But, roared on by a sizeable contingent of Iran teammates and fans, Asian champion Amouzadkhali retook the lead with five unanswered points before closing out to win his first world title.
The opening bronze medal match at 65kg saw European champion Hungary Iszmail Muszukajev defeat three-time world champion and Tokyo 2020 silver medallist Haji Aliyev 4-2.
A cagey opening saw the Azerbaijan grappler go down 2-0 after suffering an early cut to the head after an accidental head clash, but he refused any major medical treatment in order to keep the pace of the bout up.
After another 2-point score, Muszukajev then demonstrated his lesser-known defensive capabilities to win the match.
The second bronze was a more exciting affair, with Sebastian Rivera of Puerto Rico initally going 6-0 up early against Bajrang Punia of India.
But the Tokyo 2020 bronze medallist demonstrated his vast experience to level the scores at 6-6, before out-lasting his opponent for a thrilling 10-9 victory.