Why did people cross the land bridge

The biggest reason was simply the fact that they were nomadic; they didn't have an actual "home" per sae, so in result they followed their food sources, because if they didn't they would have run out of food.

Do you have more info about it ? i doubt this is the answer because i don't have all the information but if trouble was brewing in a clinic maybe it was an argument as to which clinic was better or smth of that nature