[Buffybuffy]

Not purely luck.
Need to have some knowledge on physic

I have played and spent enough to tell luck is one of the factor many favors. 
 
Setting of the claw (grip)
speed of retraction of the claw
speed of the moving of X or Y axis
spinning degree of the claw when lowering
Shape of the toy
How shallow or tall the chute wall is. Tall means must lift up then can drop into the chute. Shallow then can drag not so much lifting.
Lastly luck.

I ever caught it in 1 catch where it was an actual catch aka 100% grip. Also have got try before at 4th try got 2 toys at the same time, the big claw machine.
I have also tried before catching 30 over times and not catching anything.

Some claws are simply no grip at all. This with skill also no use one. Must be lucky then get the 100% grip.