Why lead someone on?

I dated a guy for 4 months and for the first time in years I felt secure and was able to communicate my needs and I felt like this is what a long term relationship should feel like. Two weeks ago the guy ended it saying he wasn’t feeling the sparks whilst he felt safe in this relationship. I even went to his family home and felt like we were building something. Why would he even continue dating me for 4 months when sparks is something you figure in the first few dates? Also for me personally sparks is a nervous system response from anxiety.