Because he's actually socially liberal for the most part, and Cruz is a religious wacko. Beyond immigration and soundbites, Trump will not fight against gay rights (despite what your have heard), recognizes planned parenthood does good things, and is in no way guided by the bible, as Cruz is.
The fact that reddit has been misled into believing he is a racist, Hitler-like candidate, haven't actually looked into what he is saying.
He is being slammed because he isn't part of the political world. Republicans in the system hate him because all of their political career ass kissing doesn't mean they will get any special favors if he wins. Democrats hate him because he is vying for the Republican ticket.
Truth be told, he is the most moderate candidate running. He isn't guided by Jesus, he doesn't owe anyone any special favors. The free trade deals are killing the US workforce and no other politician will approach it. Her isn't against health care policies, but anyone with a job will tell you how horribly the Democrats have dealt in implementing such policy. It was a disaster. We have borders like all countries, yet people have deemed citizenship a race issue, which most people see through, as untrue.
The more the establishment screeches and tries to attack Trump, the more obvious it is that they are afraid their entire career of ass kissing and favors are slipping away from them.
No matter your position, anyone that thinks Cruz is better, is insanely and dangerously religious. Modem republicans hate this false correlation, and Trump is an example of that. The cheesy attacks are often untrue, by opposition, and it drives Trump supporters further, hence the record turnouts.
The media has last control of information, and Trump is too public to smear without evidence to the contrary.
The scariest candidates go as follows in order from least to scary :
A:) Kasich
B:) Bernie/Trump (same category )
C:) Hilary Clinton/Marco Rubio (same category)
D:) Cruz (scary bible thumping lunatic, won't change, believes the bible literally)
Marco