I could tell a story from a typical mainframe client decades ago. This was successful big distributed corporation, which begin, when mainframes was only viable

I could tell a story from a typical mainframe client decades ago. This was successful big distributed corporation, which begin, when mainframes was only viable technology for them, and all their business was inside machine. They grow decades, but once happen problem - mainframe reach it's limits, and vendor was not agile enough, and said "we will transfer all your infrastructure to new hardware, but in few months" (they understand this as will stop business for long time). I don't know all exact details, all I know, other company made them offer, claimed they will transfer to cloud, without stopping work.