"Can a company that's not even close to profitable be considered a "market leader"?"
Sure it can. Uber and Twilio are generally considered, far and away, as market leaders in their respective spaces; Uber is massively unprofitable and Twilio was operating at a loss at the time of its IPO.
Market leadership is a function of production and capacity, not profitability.
Do you compare all usage, or just their hosted versions (i.e. do on-premise installs count)?
Do you compare all usage, or just paid usage?
Can a company that's not even close to profitable be considered a "market leader"?