It was simply a technology bubble. In the 1970s...everyone felt that solar would arrive one day. Well...by the late 1990s...the crowd felt solar was now on the verge of arriving and delivering a massive contribution to society. They guessed wrong. Solar has yet to arrive.
When your entire house can run on half the amount of power that you currently consume....and the solar apparatus on your roof can deliver one-hundred percent of what you need at least 200 days out of the year....then it’ll amount to something. Today’s just not that day.
The only viable green energy is hydroelectric so naturally the greenies are desperate to tear out as many dams as possible.
At best, solar panels can be purchased at $4-5 per watt, IIRC. The commercial efficiency is about 15%. Laboratories claim efficiencies of 30% to 50% (that and $4.50 will get you a Frappuccino at Starbucks) . The real improvement over the years was in the durability of a panel; the warrantees are into 20 years, again IIRC.
The breakthroughs that the market was and is waiting for is in cost of manufacturing and efficiency. Bring the cost per watt down and get more power out per panel, and all the while keep the quality/longevity the same. We are still waiting. Of course, if you can bribe an "expert" in solar energy to endorse a new manufacturing process, you too can get a huge govmint subsidy.
The math: with an average electric bill of $200-300 a month as the method of recouping any costs ideally ($12, 000 to $18,000 over 5 years), how much is a homeowner willing to spend up front? The numbers are actually less attractive.