It is difficult to explain why people would embark on a 5000km trek along a dangerous ice bridge to a continent that they did not know existed.In the Beringia region migrants could see mountains in the distance.
I don't think they went on a "5000km trek along a dangerous ice bridge to a continent that they did not know existed" as if it was a conscious decision of a people to go to a far land. That's an almost biblical scene. Certainly worthy of a Hollywood B-movie. The Solutreans couldn't afford the luxury of such romantic fantasies. In their daily struggle to stay alive they were totally preoccupied with ONE thing only:
food !
I submit the Solutreans hunted seals and penguins. Excellent high-caloric prey. And like all good hunters, they followed their food. And lived on the sea ice shelf exactly like the Inuit do/did: their entire lives. For generations. Centuries even. And then, one day, on one of those thousands of daily hunting trips, by pure accident, they landed in America.
America was a land of plenty, a 'paradise', to the Solutreans: it still had the megafauna that the Solutreans' forebears on the European mainland had so effectively made scarce – not much later leading to extinction*. This scarcity had been the very reason for the Solutreans to start hunting seals and penguins a couple centuries before! They
had to.
Neccessity is the mother of invention.
Everything else is either evolution and/or pure coincidence.
(One and the same of course)
* BTW, this megafauna extinction may be the first incidence in hominid history of an environmental disaster caused by human pressure...
BTW2: since then, penguins have also become extinct, in the northern hemisphere. Seems likely that human pressure was a major 'contributor' to that process too.