Is Bernie actually aware that there are other circuit designers other than Tilke?
He probably is, but Tilke has two things going for him:
1) Experience. Tilke has designed twelve circuits (Bahrain, Sepang, Shanghai, Istanbul, Valencia, Singapore, South Korea, India, Abu Dhabi, Austin, Sochi and now New Jersey) and redesigned six circuits to various degrees (Barcelona, the Nurbrugring, the Hungaroring, Hockenheim, the Red Bull Ring and Spa). Plus, he's got a whole host of other circuit projects that will not host Formula 1. No other circuit design firm - Apex and Populous being the most prominent (though Mark Skaife has done several for V8 Supercars) - has as much experience. And Populous' redesign of Silverstone's "Arena" configuration is the only non-Tilke change to a circuit on the calendar.
2) Services. Tilke isn't just an architect. In fact, he's not actually trained as an architect at all - he's a civil engineer. Tilke GmbH is a civil engineering, architecture and construction management firm. When Tilke gets a contract to design a circuit, he sees the entire project through from the initial surveying of the site through to the official hand-over of the circuit to its owners. it might sound anti-competitive to have one cmopany do all the work, but it actually streamlines the entire process. The only circuit he has not done this for is South Korea, when he did not manage construction, and that very nearly didn't get finished. In fact, it was only completed when Tilke took control of the project in the month before the race. As far as I know, Apex and Populous do not offer these services.