Another aspect to the bubble that is rarely (if ever) mentioned is the all the work that was happening in parallel for Y2K.
Every major company updated their infrastructure at the same time based on the over-hyped threat of a date format change. All of that simultaneous spending allowed new tech companies to show projected revenue in an attempt to justify valuations.
It also allowed systems within an industry to be updated in lock step which was really convenient for things like price fixing.