I'll try to describe how the hydraulic clutch works without putting you to
sleep,

The hydraulics work very much the same as the brakes work. You press the
brake pedal, this pushes fluid through the master cylinder and into the
brakes, which do what they do. If you sit at the stop light and press the
pedal, and the pedal sinks, then you are pushing fluid around internal seals
inside the master cylinder, and the brakes remain activated at whatever the
level is, but your foot slowly sinks to the floor. When you have this
happen, you need a new master cylinder. There is no leak to the outside
world, but the MC is said to be leaking anyway because the leak is internal.

The clutch works the same way, with an important exception.

The pressure plate inside the clutch plays the roll of your foot pressing on
the fluid. You can have a "leaky" clutch master cylinder (leaking
internally), and the pressure plate will not disengage from the flywheel
more than about 2mm  or 3mm. The result will be that the clutch engages the
flywheel while the pedal is still very close to the floor. If you stopped
your car or truck at the red light, and left the transmission in gear and
the clutch pedal held to the floor, it is entirely possible that the
pressure plate springs will push the fluid backward through the system and
result in the vehicle creeping, or the pedal will be far closer to the floor
after a traffic light than during a normal shift. A test is to pump the
pedal a few times, hold the pedal down, select a gear and see if the pedal
comes up from the floor relative to what you think is "normal" for today's
standard -- you said the pedal was close to the floor, this is the new
normal, if you pump the pedal a few times does the pedal come up to the old
normal?

If pumping the pedal a few times raises the engagement point from the new
normal to the old normal, then you need a new clutch master cylinder. This
may or may not be related to prior service -- my judgement is that if you
need a new MC, you needed one when you had the service done a couple of
months ago. If pumping the pedal results in the new normal remaining steady
and constant, then there could be an adjustment down on the side of the bell
housing that adjusts the clutch fork position to remove some of the play. If
you can adjust the play out of the clutch fork, the pedal will come up from
the floor. It is possible that when they serviced the fluid, they also
adjusted the play in the fork. Normally it is not necessary to adjust the
clutch fork, and it is common that the clutch fork won't have an adjustment
screw on it. But if there is an adjustment screw, the adjustment is easy to
accomplish -- it's also easy to adjust improperly.