You need to look carefully at how it's measured. One of the major contributors to data rate is availability: with low Earth orbit satellites they might only have a few minutes of downlink opportunity each 90 minutes. With relays, constellations and/or networks of ground stations you can increase that availability of downlink up to 100%.
Technically there is a limit given by the modulation technology: whilst the infrared carrier frequency is around 200-300 THz, the switching of the beam is usually less than 40 GHz, though 100+ GHz switching does exist. You can 'switch' amplitude, switch polarisation, switch frequency, or simply turn the light on or off, or do something more fancy with multiple overlaid modes.
It matters how data is encoded. In theory you can get more than 1 bit of information from just one photon, e.g. by using pulse position modululation (and encoding information in the timing).
Another factor is how much error correction code you need (like Reed-Solomon code). You send redundant data, for error checking and correction. The noisier the channel (i.e. more atmosphere or the less power used) the more error correction you need. That reduces the data rate. Or on the contrary, boosting the power and the link margin means you use less error correction and get a higher data rate.
Another factor is how many channels are being sent. You could in theory send multiple channels along the same path, or via having a satellite or ground station with multiple lasercom terminals.