Hake Stone was ultimately persuaded by Amberser, although Amberser hadn't even built an Alchemy Factory, not to mention the ridiculous talk of reviving Alchemy City. However, Hake Stone was willing to take a gamble.
The main reason was that he had made a fortune from excavating the underground city before, and now he could afford to consider it an investment, even if it resulted in a loss.
Additionally, Amberser gave Hake Stone the impression that he could pull off even the most preposterous stuff.
Paladins bowing to Liches could become a reality, so reviving Alchemy City, who knows, might actually be achievable.
Having lived many years, Hake Stone had witnessed the rise and fall of various nations across the continent, and he also knew that the decline of Alchemy was temporary. Sooner or later, a new era of Alchemy would dawn.
Investing in Amberser ahead of time could turn out to be a highly lucrative deal.