Answer:
They evolved on land to begin with from earlier now extinct groups groups so there was no need to adapt to life on land, other than to adapt to different terrestrial environmental pressures. Land can be everything from next to a river to a hot desert to rocks to Antarctica, and plants grow in all those places.
As well, there are thousands of species that are floating aquatics or submerged aquatics, including many ferns, and even some gymnosperms grow as marginals, and many species of angiosperms, mosses, ferns, and even some gmnosperms grow as epiphytes, or as parasites, or other ways.
