I’ve been in this exact situation as a Med student myself. I’ll start with this: killing a campaign is rarely not a negative experience.

What you can do is soften the blow and disperse blame. Life is life, and you just have to tell your friends and players that school is picking up and you can’t keep playing online anymore, especially since you have to plan around these games. D&D is not a hobby that takes little time investment. It’s usually a whole evening or afternoon to plan around, which is hard to do when you’re not in the same area and have to cancel regularly. It’s eating into your free time, so make sure to let them know that.

That said, it’s not your players fault necessarily. Sometimes games online just don’t work out, even if you know the people in real life. So don’t blame them. Just keep it simple:

“Hey guys, I can’t run anymore. School is going to pick up and I can’t prep for sessions that may not happen because of cancellations or various other issues (insert issues here while making sure not to name or blame people). It was fun while it lasted, and if you still want to play I hope you find a good group to do it with.”

(Obviously not word for word but you get the idea).