The brother of
Martin Lel (a former winner of the
London Marathon), Kotut began to compete in professional
road races in 2012. He placed fourth at both the
Portugal Half Marathon and the
Marseille-Cassis Classique Internationale that year. At the start of the following year he travelled to the United States and took third at the
Mardi Gras Half Marathon, but an attempted debut at the longer distance ended in a failure to finish at the
Linz Marathon. A career breakthrough came at the
Philadelphia Half Marathon in September, where his time of 59:59 minutes brought him runner-up spot behind
Stanley Biwott. This gained him his highest global placing yet, at twelfth for the season. Kotut ran on the 2013–14 Spanish cross country circuit and won at the
Cross de Venta de Baños and the
Cross Zornotza. He also set a best for the
10K run of 28:17 minutes to win the
We Run Rome race. He competed sparingly in 2015, but still performed to a high standard, with runner-up finishes at the
CPC Loop Den Haag and
Milan Marathon (2:08:55 hours). Two victories came in Paris for Kotut at the start of 2016 – his first wins beyond the 10K distance. First, he won the
Paris Half Marathon, then topped the podium at the
Paris Marathon. He recorded a personal best of 2:07:13 and easily beat the runner-up,
Mark Korir, who had entered as defending champion. The sudden win at a high quality race was unexpected for Kotut, and he remarked: "I had prepared well but not for this victory. It’s a surprise for me." In 2022, he won the Hamburg Marathon in a personal best of 2.04:47 beating the course record of Eliud Kipchoge from 2013. In 2025, he finished third in the
2025 Boston Marathon, in a time of 2:05:04 ==Circuit wins==