There are a lot of variables and quite a few different situations with tubeless, but in a nutshell: seating the tire's bead depends on air pressure being in the tire. The tubeless tire cannot become airtight until this happens. An air compressor floods a high volume of air into a tire very quickly, gets the bead seated, and the tire becomes airtight as a result, and inflates. Initial inflation with a tubeless tire, using a floor pump, is difficult in most situations, if not impossible. You can't get enough air into the tire fast enough for it to become airtight and inflate. In most cases with a floor pump, you just pump air right out beneath the tire's bead.

There are exceptions, and on more than one occasion I've been able to pump up tubeless tires from scratch with a floor pump. You can't depend on it, though, and it can be done, IME, only with tubeless-specific tires and rims.

Keep in mind, once you get tubeless tires inflated, they can be topped off with a hand pump, no problem. It's the initial inflation, getting the bead seated, that's often tricky. Soapy water on the tire's bead, etc is a good idea.