iphone videos blurry/FCP. please read!!

so i can send a 5 min 4k video from my iphone to a friends iphone and it comes out crystal clear. however when i transfer the same video to final cut pro and just do small editing along with cutting the time down to 2min and then when i send it back to my phone by air drop its crystal clear on my phone but when i send it to another persons iphone it then comes out blurry and small. i even cut the video down to 10 seconds to see if length was a problem it still comes out blurry and small.but i can send them the original 5min video in 4k shot from my own phone perfectly. in FCP i saved the video as a HEVC and i also tried apple devices and changing resolution several times. the only way i have figured out to to clear SOME of the blurry is by air dropping to my iphone and then moving the edited projected to imovies and then just saving it and then send it. it’s not crystal it’s slighty better. what am i doing wrong? i don’t think it should be this difficult to send a 4k video in 2024 it should just be click and send.