Why did the man cripple Jacob during the wrestling?
The man crippled Jacob because he could not overcome him in the wrestling match. When he saw he did not prevail against Jacob, he touched the hollow of Jacob's thigh, dislocating it. This ended the struggle and left Jacob limping from that point onward.
Les explains that Jacob was left alone after sending his wives, servants, and eleven sons over the ford Jabbok. A man wrestled with him until the breaking of day. When the stranger saw that he prevailed not against him—that he could not overcome old Jacob—he touched the hollow of Jacob's thigh, and it was out of joint; in other words, he crippled him. From this point on Jacob walks with a limp, called a halt in Scripture. The crippling was how the stranger stopped the wrestling when he could not otherwise overcome Jacob.
And Jacob was left alone; and there wrestled a man with him until the breaking of the day.
More Questions
Who did Jacob wrestle with in Genesis 32?
The man who wrestled Jacob was God himself appearing in a theophany in the form of a man.