Takeda Machinery was a family owned business with just 4 staff. When the elderly wife of the owner died he lost interest in running the business and with no children, he decided to withdraw from the market. Rubycon had been pressing for increased orders due to the manufacturing setups required for manufacturing Blackgates and the impact of that on normal production of capacitors for computers.
He was offered large amounts of money for the license rights and declined all. Thus the end of Blackgate, no mystery, just an old man feeling lost and deciding to call it a day.