Why has he suddenly become perverted?

Me and this guy have been talking and it seemed to be going well. He was asking me nice caring questions over the last 4 weeks. Now it’s gone weird. Last night he started asking me what my thinnest pair of leggings are. I told him I felt uncomfortable talking about my leggings and he just wrote back and told me that I’ve got nothing to feel uncomfortable about. He carried on asking me about my leggings. He’s interested in gym and we were having a nice chat about that, then he went on about my leggings. He asked me to send him a pic of me in leggings because he wanted to see my gym progress. So i sent him one. He then asked for another pic of me but without leggings, just me in my pants showing my ass. I got the impression a few weeks ago that he wanted a romantic relationship because he was asking me questions to get to know me in a normal way, now he’s started being perverted. I nearly blocked him earlier because it started to get to me but decided not to. Any ideas why he’s being like this?
Why has he suddenly become perverted?
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