You'd be surprised by how many bookers actively look for a pantomime villain, particularly if they can be surprisingly amusing with it.
My industry's UK association for example is one that relies heavily on ever closer unity of nations across borders, ease of movement, ease of trade etc. Devolution of nations into ever smaller ones is not something that does us any favours, so it was something of a surprise to go to an industry dinner and find that the speaker was Alex Salmond (albeit "pre-sex-allegations Salmond", I'm sure he's in lower demand just now). It was a surprising booking precisely because of how contrary he was to our aims, but because he spoke about our aims and was witty about it, he went down a storm.
I suppose it's the difference between being interested enough in your audience to do your homework, and relying on being a blagger to see you through (as per the Jeremy Vine anecdote about Boris's pre presentation speeches). To be an effective blagger you need to have a good enough memory to remember which version you have presented to which audience, or else they too will begin to ask, "is this guy for real?" This pre prepared simulated spontaneity might have worked for him when he was able to avoid scrutiny but when he has to stand up and be scrutinised he doesn't do too well.
He noticeably became hard to find as soon as he took office, after his shenanigans leading to the "Oven Ready Brexit Deal" which now appears still to need many of its ingredients, let alone an oven. Most readers of this thread will have been interested enough to sit through Prime Minister's Questions, and seen the way he embarrassingly blusters, diverts and throws out blame rather than makes a serious attempt to answer the opposition's questions, for example. Let alone the various u turns to which he has been party during the COVID-19 pandemic. He may blame others for their part in these but ultimately he is Prime Minister.
I can't help thinking that once Cummings has gone, and Brexit officially takes place on 1st Jan 2021, with or without a meaningful deal, Johnson will soon follow, leaving a new leader to try and sort out the resultant mess.