To delete a large list of inactive Collectors you will need to use the Collector Management API. With the API you can get your listed Collectors in JSON format and then parse the Collectors and find the IDs where the parameter "alive" is currently "false" and has been false for a time period greater than some number of hours say "X". You can then call a delete request to the API to delete the Collectors. I have referenced a public Google doc at bottom that contains a sample python script which will list and/or delete (with suitable updates) any Collectors that are offline in the account for more than X hours. Care should be taken to validate that the inactive collectors deleted are not temporarily offline.
Note: this is an unsupported script and is provided as is and only as an example. Also note that
Here are some documentation links for the API commands
To prevent this buildup of old Collectors for example in an AWS environment, you might consider including the "ephemeral=true" option within your sumo.conf file used with the automated install. This option will make sure the Collectors are automatically removed after a period of being offline (12 hours)
Once you have cleaned out all the old Collectors we would also highly suggest upgrading all your current active Collectors to the latest version of the Collector and also update your install scripts to use the most current version as well. The latest Collectors are much improved from the version you are currently running and include many updates for better performance and reduced resource utilization.