Wow, Stewart Butterfield had just ONE HOUR of total face time with Marc Benioff before Salesforce announced its $27.7B acquisition of Slack, the second-largest software acquisition in history at the time. “My last meeting with him was cut short because McConaughey arrived.” Stewart left the company after 18 months; he says the tipping point came when he was invited to Davos to represent Slack and Salesforce. Thinking he would be there to talk to customers, he instead found himself scheduled…