Why don’t guys talk to me for a while if I initiate they reply but won’t continue to talk why is this?

There’s this guy that seemed interested in me when we first met and then stopped talking after about 20 days and he hasn’t talked to me too much sometimes I try to talk to him and initiate first and he replies but doesn’t keep the convo going too much I asked him a question he answered we talked about it and than he asked me how I was we talked for a little bit back and forth than he left me on open and stopped. I’m glad I heard from him a little bit bc I thought he’d ignore me but he didn’t.. so my question is…
Why don’t guys talk to me for a while if I initiate they reply but won’t continue to talk why is this?
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