The map is updated during a month, so you need to fast forward a month. Each traveller is generated by a random function, hence some number vary from month to month. Extended passenger generation is vastly different from the standard Simutrans.
For Simutrans for each passenger generated (the number depends on the level of the building) a certain percentage are factory workers (how much depends on the number of surrounding factories, size of twon etc.), Next another percentage are tourists. For them a random tourist attraction is chosen, the higher the level x area, the more likely a destination, and nearer are also more likely than far destinations (this changes over time). For the rest a random city is selected, again larger cities and more close cities (including the own) are more likely destinations. (The preference for nearby destinations decreases again over time.)
For you map, you should first make an inner city network in the largest town, with one large connection hub. Since this is by far the largest town, it will be the most likely destination of every passengers, including the ones in that town. Then connect this town to nearby larger cities, for instance the cluster to the bootom right looks promising. When you starting to transport passengers (and mail), some of the red overlay of no route turns more and more green (and yellow, if your stations overflow).