Really depends on the phone and how the controlling organization (whether it's a private company or the IDF) uses MDM/MAM. It's totally possible to poorly manage iPhones, and if you do they'll be insecure as hell. If you were to restrict everyone to a specific Android phone model with hardened software, then you could theoretically do better than deploying all iPhones. Hell, you could even put GrapheneOS on them, but that would be quite an undertaking, and I'm not aware of any company doing it at scale.

Because of the homogeneity of iPhones and how strictly Apple controls them, it's generally simpler for organizations to manage them and ensure all of their employees are using updated software on a relatively secure phone. So that (in my opinion) is why we're seeing a lot of organizations just say "screw it, only iPhones allowed".

anymore details on how they deviate? what specifically is more secure about an iphone than an android?

Feel free to go into deep details if you have them or links

It's secure if you're not stupid and you don't turn off the safety protocols it literally warns you not to turn off. Stupid people need apple's domineering control to protect them from themselves