With regard to Dyson and Juncker it seems to me that there is an essential difference between them in that Dyson, as head of the company that he created, has an absolute say in what the company does whereas Juncker doesn't. He has to persuade the heads of government and the European parliament to go along with his ideas. Any one country can frustrate his plans by exercising their veto.
Juncker was not a popular choice for President of the Commission; he only got it, it seems, by some tricky political manoeuvring and the reluctance of other possible candidates to stand. This would indicate that he would find it hard to bend the EU members to his will.
In one of the first lectures of my politics degree we examined the question of 'Where does power lie in politics/government?', The conclusion was that it is difficult to pinpoint a single entity as exercising absolute power. While we were looking at this in respect of the UK government it applies equally to to such a large and diverse organisation such as the EU. It is unrealistic to believe that one man alone can exercise absolute power over it.
And, of course, the belief some people have that Juncker is 'Mr EU' is at odds with the belief that others hold that Merkel is the ultimate power in the EU. An illustration, perhaps, of the difficulty of pinpointing exactly where power does lie.