Answer:
food supply was great on land
Step-by-step explanation:
The ancestors of the amphibians started to explore the land and evolved gradually into the first amphibians because of one main reason, the food supply was great on land. Not just that the food supply was great on land, but there was also no competition, so pretty much every niche in the food chain was free was taking. Apart from having no competition for the food sources, there was no predators as well, so in general the land was the best environment there was for living at the moment and they tried to exploit it.