Firstly, in order to remove delve, the option is actually hidden in the SharePoint admin center. So you need to get their by going to your office 365 admin. Then selecting the admin centers tab and choosing SharePoint Admin Center. You will want to make sure you are in the classic experience so that the settings look the same.
Once you get inside of the SharePoint admin center you need to click on settings. Inside settings there is an option that says “Delve powered by office graph” you just need to disable this on the right and then apply the changes. This can take up to 10 minutes for the app to be removed/hidden from your users. If you go back to office 365 and browse all apps you will notice that it no longer shows up in the list of applications.