What caused Frodo to finally give in to the power of the Ring and claim it?

one does NOT posses the Ring, the Ring posses you. for Sauron's Ring is but a tool to corrupt and ensnare the other races to his will. like a drunkard or an addict, forgive the poor allegory, will say "I can stop anytime i want. I am in control."

these are but lies and self-delusions that comes with possession of a thing only to corrupt and destroy, it does not matter how righteous one's intentions are...beautiful yet utterly terrible. what caused Frodo...? the Ring. It's powers are beyond any mortal or immortal beings on Middle-Earth.