simple people over simplify answers. money was one factor. but his outreach game sucked. he embarrassed himself in nationally visible ways (fire alarm). he took hard stances on divisive political issues (Israel/Hams) when his constituents had divided opinions. he district was redrawn so he lost part of his base.
I hate this divisive bullshit. Democracies require pluralities. You need to be a big tent party to govern.