Why does Ex acts weird?

Ex and I were stuck in a theatre sitting next to each other. All the while he didn’t talk and neither did I. We both ignored each other to the best.
When his friend asked about me he said ‘We used to talk but not anymore’ very casually while he was the one who didn’t want anything. I dismissed it. J did notice my ex checking on me every other minute.

Then I saw him viewing my LinkedIn profile out of nowhere.

Why does Ex acts weird?
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