"If I'm going down, I'm taking you with me! Bwahahahahaha!" Although, it might just be an excuse not to invite you to the retirement party.

That’s one boring bucket list he has...

Two birds one stone?

He probably knew that you wouldn’t be happy working for his successor, so he mercifully set you free. Yeah, let’s go with that!

Well, it would be poor form to retire before the job is finished.

You should have used a colon instead of a period after “retired.” Hopefully, your job did not require a firm grasp of grammar.

At least he saved the best for last...

Just show up tomorrow, ala George Costanza. Your boss won’t even be there to say, ‘What are you doing here? I fired you.’

Maybe you are the best employee there and he wants it to look like the company is failing after he leaves so they always remember him...

Realistically, I see two possibilities: Either the retiring boss did it at the request of his upper management who wanted OP gone. In that case the retiring boss did it so the new boss wouldn’t look like an A-hole. In that case maybe the retiring boss didn’t really have his heart in it. Or, the retiring boss really didn’t think much of OP, and this was his parting shot. Either way, OP needs to be concentrating on finding a new job and improving their skill set and communications so the next job goes better.