Please don't misunderstand me; I'm not saying that anything Bernie actually *earned* shouldn't be his. And I'm certainly not saying that Trump's net worth wouldn't or shouldn't seem crazy (using your terminology) to the average American.
My point is that to characterize Bernie's net worth, in comparison to the average American's, which for their age group is about $1 million dollars less than Bernie's, and to then say Bernie's net worth is not so crazy, displays a certain detachment from the financial reality of every day Americans.
And that is exactly what I would tell to those living paycheck to paycheck, and you!
For someone who has built his political career exploiting income disparity, doesn't it seem odd that Bernie has a $450K home in Burlington, VT, (wow! check it out, here: https://virtualglobetrotting.com/map/bernie-sanders-house/view/google/) and he also owns a home in DC, that is worth about $560K. That's over $1 million worth of homes that he bought *BEFORE* his book deals. And of course, his new home is worth about $575K.
So, to answer your question about why he's attacked for his wealth when Trump isn't, I think there's a couple of good reasons. First, Bernie is a self-proclaimed socialist, and Trump is obviously a die-hard capitalist. I would hope the capitalist is worth waaay more, and I think most people agree, which explains the perceived lack of criticism. Although to say Trump's not criticized for everything about him, is possibly disingenuous.
Also, it's because Bernie attacks the wealthy, even though by any reasonable standard, he is quite wealthy. It's the hypocrisy of it all... the hypocrisy. As a socialist, why doesn't Bernie practice what he preaches, and give away all of his fortune to the poor, except what he needs to live on?