It's simple: the Republican Party was offering more handouts and freebies at the time than the Democrats. People were told by President Jelly Belly that they could receive massive amounts of tax cuts without ever having to pay for them through spending cuts; the modern Republican Party, its explosive tendencies of debt accumulation and the beginning of our debt problems were born. The older generation at the time - accustomed to voting Democrat - could jive with Reagan's message of "we'll give you more social programs and more money, but the only thing standing in the way of doing that are all of these welfare queens and young bucks". Herego the Reagan Dixiecrats.
Of course, the concept of selfish entitlements and a "me, me, me" attitude rang true with the Baby Boomers, who have no doubt been the worst generation of human beings ever to walk this planet. The attitude shift wasn't one of maturity, but rather one of embracing the next phase of selfish entitlement in their already-privileged lives. In the 60s and 70s, it was all about protest culture and free love because that's what kept their asses safe and out of war. Unlike their parents - who actually knew hardship - when they started working, they wanted to keep all of it for themselves. That mentality has recently gave way to the desire to cut and cut and cut program after program to preserve their own entitlements as they draw nearer to Death's Door, and is the only response/solution to a lifetime of them pissing away everything every previous generation worked so hard to build. Truly an entitled bunch, from the cradle to the grave.
In summary, a combination of all reward and no sacrifice, massive amounts of credit fueling unrealistic and unsustainable economic growth/the ability to live outside their means, and the promise from Reagan and Republicans to deliver on all of that - backed by strong-arming the vulnerable Democratic caucus into acquiescing - was what pushed the selfish and materialistic Baby Boomers into the Republican Party as their generation began voting en mass. The "Reagan Democrats" play a part, sure, but it was the sway of the Baby Boomers that created the political climate of the 1980s. Now, they're freaking out because they see the Millennials beginning to rip their electoral power away from them and restoring the country to the economic principles that existed before they spent a lifetime plundering it. Here's to hoping they won't get to spend their final years doing what they've been doing for decades.
Methinks this rests upon to many generalisations
Anyway, whilst I'm obviously no expert, my tuppence on this is that, basically, a lot of people were rather enthused by the Republican party's message in the 1980's (lower taxes, fighting crime and drugs, 'toughness' when it came to foreign policy), whereas the Democratic party failed, really, to offer a compelling alternative. I mean, from what I've read, the campaigns of Mondale and Dukakis were pretty stale and flat, offering little in the way of inspiration. Also, the less than brilliant record of Democrats in office during the late 70's was a bit of a millstone around the party's neck (and a memory that would be resuscitated to great effect by the Republicans throughout the 1980's).
