Why would someone follow and then unfollow on instagram?

So my ex reached out to be after a year for saying sorry and how much he regrets cheating on me and I found out that he was suffering from cancer and now is better so we talked on call briefly about his health conditions and then he asked me to meet to which I agreed , and he asked me if he could follow me back on Instagram and I said yes so after that he did not plan anything to meet me as he said he will meet me once his hair looks better after cancer treatment and after 15-20 days unfollowed me from gram. I don’t understand this.
Why would someone follow and then unfollow on instagram?
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