A Semicolon Rule

Semicolons are rather like strong commas and weak periods. The rhino geek below makes a point that’s usually true. Semicolons are supposed to connect two independent clauses that are on the same topic. In other words, closely related sentences. Independent clauses don’t usually start with a conjunction. 

https://www.gocomics.com/saturday-morning-breakfast-cereal/2018/12/18

The rule about conjunctions is a bit mechanistic, though usually it’s correct. Too bad for him.