Cassara gradually became frustrated as the 2018 World Championship silver medallist went on the defensive and Kruse had enough to claim a 15-11 victory and lift his first Bonn World Cup crown.
Speaking after the match, Kruse expressed his delight at finally clinching an elusive eighth World Cup title.
"I'm very pleased to win the World Cup in Bonn," he said.
"This was the only world cup I hadn't medalled in to date so I'm pleased to have changed that. This pushes the tally up to 8 world cup victories, if I could make it to 10 then I will be able to retire happy!"
His coach Ziemek Wojciechowski added: "This is the eighth victory for Richard in World Cups and Grand Prix events.
"It is incredible to see Richard showing yet another dimension of his mastery in defence by using more then ever a variety of actions from the line."
The four-time Olympian is only four points off taking the much coveted world number one spot as Tokyo 2020 qualification begins to take hold this season.
The Chatham-born trampolinist tweeted: "7th in the World, 5th World final, oldest competitor, I'll take that. Proud of Luke Strong for making his first world final."