I watched a programme last night about Hillary that said she'd defied the Secret Service and only used her own email address rather than the specified one, for all her official emails, and here is the clincher, thereby bypassing the Freedom of Information laws.
this is a big factor -- there were i think 3 email (out of tens of thousands) that had details of classified or secure information that may have impacted ongoing operations or put government personnel in harms way should the emails have been accessed by someone they weren't meant for. This was apparent;y more likely from her personal server that than the 'secure' government one. (hello wikileaks)
she is seen as 'the establishment' due to her history as first lady and the connections that brings (no mention of the experience that brings, and discounting her experience as senator for NY and sec of state.)
related to above -- she has taken campaign donations from 'big business' so is thus seen as being 'owned' and beholden to the banks and pharma industry (the republican party being practically owned by the NRA is apparently different)
she voted for the Iraq war (as did Trumps VP nominee, but apparently that's ok)
it's a disgusting mud slinging shit storm from the republican party and Trump who is a childish, name calling, dangerous bully -- example of merchandise being sold last week outside the Republican national convention: