Just because an idea is stupid today doesn't mean it won't be a everyday thing tomorrow.
And just because "they all laughed at Einstein" doesn't mean that your stupid idea is correct.
I highly doubt you would be all for spending this money researching whether we can create roads out of ice cream simply because "it might work!". You'll go broke very fast funding every crackpot with an idea.
Plausibility MUST be a factor in determining where to put money and time. And solutions that are already better in EVERY way already exist (just put tilted panels along the side of the roads). And those options will always be better since they don't need to work around the constraints.
Solar roadways is not an experiment - it's a con.