Tinder removed the IG handles more likely because men were stalking women’s instagrams and it wasn’t immediately obvious connecting to instagram was going to display your username for all to see.
Bumble did it for that, probably not tinder. Most people who put their insta expect others to be able to add them on insta. This is the whole point of insta, it is to have the most people as possible watching at you. Tinder has always struggled to keep users in their app, which is the most important goal when you are a social network
Tinder is still there for the "discovery" of the people to add on Instagram, that is not going to change. Tinder doesn't make any extra money after people match, whether they continue to chat in or out of the app. Once connections are made and the users move out of the app, they still come back to Tinder for more discovery.