Somehow he had to know that Charming and Snow White would continue to find each other. The finale makes it clear that he wanted this to happen, and so he helped it along when the chance presented itself.
Snow came to him for the potion to forget, so he got her hair
Snow came to him to kill the EQ, and he got Charming’s cloak with his hair when he came to find her.
The bow and arrow he gave SW found it’s mark and provided the opportunity for Charming to restore SW’s memory of him.
Then he met up with Charming and coerced him into a deal, not because Charming was particularly desperate at this point (although he would have become so after some time), but because Rumplestiltskin needed them to find each other at this point. He needed what their “true love” would produce — Emma and I also think the powerful magic of true love.
How did he know to await Charming there? The queen decided on a whim to send him?
And all of that to set up our story with Emma as the savior and regain the bottle of love for a “rainy day.”