There are answers to such questions. They may not meet your criteria in the near term.
1) A lot, perhaps all, of the mutilations appear to take place aboard craft hovering or even that abduct the cattle, fly off, return to the spot or near the spot and drop the cow--usually for significant height.
2) You've not begun to explain the KNOWN factors that are COMMON in EVERY valid mutilation case. You haven't BEGUN to do that--do that and THEN ask the questions that remain unanswered.
3) Some contend that it's American Government JOINT research with ET's studying pollution and/or nuclear pollution. Others contend that those specific organs and blood products are needed in ET food/breeding/DNA enhancing . . . . whatever . . . experiments/projects.
The degree and attitude of skepticism you voice regarding the cattle mutilations just indicates to me--increasingly--that you have NOT studied the phenomena deeper than a slight surface scratch--comparatively.
Sigh.
When you're sitting in the middle of the Wyoming prairie and you hear hoof beats, expect to see horses - not zebras (or unicorns).