VBO (Views Bulk Operations) - Bulk Operations field not showing in field list
Using VBO with CiviCRM views requires the CiviCRM Entity module, so
make sure that is enabled.
CiviCRM Entity does not expose all CiviCRM entities as Drupal
entities by default.  Go to
admin/structure/civicrm-entity/settings to enable the right
entities - in this case, Contributions


(Thanks to @jackrabbithanna on chat: https://chat.civicrm.org/civicrm/pl/85qwezc5d3fo3jr4hxgafoyn4r)