Most thoughts on the whole matter can only be seen as speculation, even by most journalists. If I was to hop on the speculation bandwagon, I'd say maybe Eric championed the Renault switch. It was common knowledge that the shareholders, Mansour Ojjeh in particular wanted Honda dropped after the disappointing pre season testing. But for them to believe it was all Honda issues, they would have been told. Like someone posted yesterday, Eric presented the data (possibly on reliance of info from Goss) and said "we would be winning races if not for Honda".
Mansour swung into action, believing his very good relationship with Mercedes (at the top) would help secure the deal. I know I've read somewhere that the Mercedes bosses were open to the idea, but Toto wasn't. I also read somewhere that Toto wasn't keen because Mclaren wanted a Works level supply, which Toto shot down. Then there was the half hearted attempt at getting Ferrari, but that was always going to be unlikely.
Now, where I speculate that Eric came in is pushing for the switch to Renault. Maybe Zak, Mansour etc had settled to stick with Honda, after failing to get a deal with one of the big two, considering all things, not least the $100M from Honda. Maybe Eric then put Renault forward, insisting on his apparently dodgy data that they would still win with Renault, guaranteeing that the late switch would have minimal disruption on 2018.
Like I said, I'm only speculating, like a lot of us are doing.