Following his standout performance in midfield, Ndidi received a rating of 7/10 from Sky Sports.
The win allowed Leicester to extend their lead over the relegation zone to four points, breaking a six-match winless streak.
Meanwhile, the loss added more pressure on West Ham manager Julen Lopetegui, who was greeted with chants of “you’re getting sacked in the morning!” from the club’s own supporters.
Jamie Vardy gave Van Nistelrooy’s reign a strong start, scoring the opener in the second minute.
Vardy’s goal was initially disallowed for offside but was upheld after a lengthy four-minute VAR review.
West Ham responded strongly to going behind, with Danny Ings, one of five changes made by manager Lopetegui, coming close to equalizing. Ings’ header hit the woodwork following a deflection.
The pressure kept mounting on the hosts, but Mads Hermansen made five crucial saves in the first half to keep Leicester’s lead intact going into the break.
Despite West Ham’s dominance, Leicester doubled their advantage with a goal from Bilal El Khannouss, just moments after West Ham had an ‘equalizer’ ruled out for a foul off the ball.
Tomas Soucek was penalized after being deemed to have obstructed Hermansen in the area before the ball crossed the line past the Leicester goalkeeper.