Fearing that Trump would expose them.
Trump has been careless in the past with confidential intel and our intelligence agencies can't trust Trump to keep secrets.
No telling what our allies are keeping from us for the same reasons. Also, what our CIA might be reluctant to share with the Administration.
The same useful idiot that thought it a good idea to bring Taliban to Camp David during 9/11 week. Thankfully, he was convinced it wasn't a good idea.
On the other hand, the implications of this development — that a US spy was extracted at least in part because the president could not be trusted to protect the person's identity — floored intelligence veterans because it confirmed some of their worst fears about Trump.