Clarkson the journo is intelligent & witty. Clarkson the TV car guy is boorish and predicatable.
Hammond the generic TV show man and Wipeout voiceover guy is likeable and funny. Hammond the TV car guy is obvious and a sap.
May the serious TV science man is down to earth and charming. May the TV car guy is dull and an apparent fall guy for old 'n' slow jokes.
That's not to say they were always like that, indeed the first half dozen series of TG they really weren't like that at all. Before the stereotypes set in, they had far more personality on TG and it was superb. I think that might have been my biggest issue with TG: All the jokes were the same, because they played on the exact same typecasting of the TG characters. The setups and locations weren't a terrible idea (indeed, the amount of work to keep them new must've been a huge challenge), but being able to see the joke coming long before it was even said just isn't the kind of TV I enjoy. Millions do, I get that, and if I'd been in their shoes I'd have carried on the same as well.
Now, if they can shift those personas a bit then TGT will be excellent and right up my street. If TG manages to stereotype Evans, LeBlanc, Harris etc then I'll be as bored of that as I was before Clarkson got hangry. Looking at it from an optimistic view though, I reckon I'm on to go from zero car TV shows of interest to two superb ones.