Sell the illusion means that he is trying to convince somebody of a lie, something that is not real. You can see the evidence for this in the fact he likes to 'pantomime' - he likes to act.

It means he's lying to make himself and the company more reliable.

Hi Baboom. I think that we need more context to give you and accurate answer. It could mean that he substitutes him to create the image of a bigger company with more employees or that he does it to bolster his image ot pretend he is in a more protagonist role.