Why didn't he pick up my phone call?

This is about my ex. We dated for like three or four days after I had enough of his shit. On the second day of our relationship, he didn't pick up my phone calls. I called him like five times. I was worried if something had happened. Then to check if something was wrong or if he was just not picking my phone call, I called him from another number and he instantly picked the call. When I later asked him, he said : he was with his friends. He could have just texted me or picked up call and said: I am busy. Let's talk later.
I am just asking because it makes me curious: was he playing games with me? Did he feel shy with his friends around? Did I butter his ego by asking him out first (technically I just asked him if he liked me. He took two days to call me and say: yes)
Why didn't he pick up my phone call?
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