“but isn’t the purpose not to avoid nisyonos but to overcome nisyonos”
Actually the purpose is to minimize nisyonos.
By teaching your son Torah you give him the knowledge to avoid sin.
(There are also other reasons to learn Torah.)
By teaching your son an honest way to make a living you greatly reduce his temptation to steal later in life.
By getting him a beautiful wife, you reduce his temptation to sin in other ways.