Frogposting will continue until morale improves!

their bodies are one giant digging muscle, if you see them digging themselves into the soil, as one giant wriggling piece of muscle it would make their bodyplan make more sense

Additionally, they can hibernate for as long as 9 months of a year, only coming out during the raining season of their respective country (hence why rainfrogs), and the lack of extremities in limbs aid in keeping mositure from slowly evaporating into the sand/soil/mud as they bury temselves as deep as a meter beneath the earth into mud cocoons

Additionally, the shit that hunts them, like owls, falcons, meerkats or snakes are not the type of shit you can be evaded as an amphibian anyways,

thus they are adapted to evade by hiding or digging to safety