I worked (in sales engineering) at such a company with a market-leading product. For a few years there, at the height of the market/mindshare dominance for their main product, I observed a recurring theme:

We'd hire a new manager from outside the company. This new manager would go around and meet some sales teams, meet some customers, then a month or two in, end up at a meeting where they gave a speech. At this speech, they would opine that customers loved our product, that it "practically sold itself" and our job was at least 90% execution.

Translation: a trained circus monkey could do your job. Just show up, answer your emails, and the product will do all the heavy lifting. Don't come complaining to me about how your quota is too high, product isn't taking your feature requests seriously, etc. Those are just excuses for poor performance.

I saw this happen a half dozen times, at least. In every case -- every case -- those people were singing a very different tune after they had been around for six months and saw what the job was really like.

Now, having good traction in the market, and analysts saying good things about you, and customers excited to be references? All that is really important. But in large enterprise sales, nothing "sells itself." And, for the record, we had plenty of people who weren't idiots, who nonetheless couldn't sell a product that was in very high demand. At least, not enough to keep their job.