You should still remove the terminals from the battery. Clean them and the battery posts. You may or may not have found the problem area but did nothing about it.

Basically what you should not be trusting is not the starter but perhaps those connections. Now if the terminals where loose enough to get some wiggle movement on them without really excess force. It points to them.

After cleaning connections putting a small amount of something like vasoline on them before assembly keeps any new corrosion from forming longer.

It was really nice to see you had a forum member come by as well.

The younger you are and the more you learn about cars the more money will remain in your pocket. Especially over a lot of years.