Why is it different with him and not the others

this might be in the wrong group but here goes nothing. Okay so no judgement here please. I am young and 100% single and living life through covid like most people. As covid has restricted alot of dating and getting to meet up with people for dates i decided that i would put that on hold and have some fun. I met the first guy in August this Last year. We both knew it was going to be a casual thing but it has all be through either snapchat or another type of communication we both keep saying we should meet up soon after our restrictions for our area (we both live in the same state but due to an outbreak some suburbs are on lockdown) so we cant meet up even though i know it wont happen which im 100% fine with cause thats what is it all about not feelings have been mixed with this guy and its just easy breezy with him. This is also the same with another 2 guys. all three guys im sorta attracted to but its fun and flirty attraction nothing more nothing less. Recently i met someone else but this time he is from another state, i know the vibe and direction he is coming from and again its causal but he is more of a casual person who wants a long term in the end. We connected straight away and again due to covid we cant meet up or travel due to the state boarders being closed. everything has been going fine until recently i have noticed that we both have been saying stuff like we would be dating but we arent. We both want to meet up and both rent going to worry about the what ifs. Genuinely he is a nice person but i have also noticed that my feelings are now getting involved with this guy. Im being very cautious cause i dont know what the hell is happening and we are practically doing the same as the other guy but more frequently i guess. why is it different between me and him and why isnt it like the first guy? im really confused why this is happening and i dont want to be that person who falls for a guy who she has never met. i have also noticed my body responds to him very intensely even though its only through a photo or video. it just makes no sense to me (i think its more lust than anything right now but i dont want those feelings to evolve) what the hell do i do ? its meant to be easy breezy not feelings or investment with them. so why this guy and why does it matter to me when it shouldnt? a side note, another part to this is ..with the other guys if they doesnt respond back until whenever i dont care and it just phases out like normal but with the fourth guy if he doesnt respond i get annoyed and wonder why he doesnt respond back. this shouldnt matter in this situation why does it? need advice please

I would seriously recommend less of a "casual sex" lifestyle. It doesn't benefit you now or in the long run.