iMovie Export Fail due to Space Issue

Hoping for some enlightenment on how iphone/icloud handles space. I do a decent amount of editing via imovie. However, when I try and export videos at times, I get the unable to export due to lack of space. When I check my local storage, I’m at about 110GB of 256. I have 2TB of iCloud storage, and am sitting at anout 450GB. With all that being said there must be more to this process. I obviously have way more than 256GB worth of data (videos mostly). But not sure how space is handled locally vs icloud. Seems it would be straightforward. If the iphone is showing enough free space, then iMovie should have no trouble exporting. My way around it is going back and deleting videos from my camera roll. But I notice that most of what I’m deleting needs to be downloaded from icloud anyway. Yet after some delitions, I’m able to export the imovie videos. Something isn’t adding up, or something I’m missing.