For a long time, a SPAC was considered to be an out-of-favor, back-door way for a company to go public. In the 1980s, these companies frequently were shell companies for penny stocks that are extremely volatile (and frequently fail). And at this time, many of these companies did just that, and investors lost a lot of money.
However, SPACs have become less controversial in the twenty-first century. Since 2010, SPACs have become more fashionable and have been sponsored by big-name entrepreneurs, hedge-fund managers, mutual fund companies, investment banks, and even celebrities.
Because of this, the number of SPACs has been increasing steadily. And in 2020, SPAC research reports there were 128 SPACs, which raised a total of $49.1 billion. The Covid-19 pandemic has certainly been a factor. SPACs tend to be a better choice for private companies in times of market volatility because they only have to convince one sponsor (or a handful of sponsors) to launch the SPAC as opposed to filing for an official IPO.
Another reason is that, unlike a traditional IPO, a SPAC has more streamlined disclosure requirements to save time and money.  This is not to say the SEC has imposed no regulations on a SPAC. The most important of them being that a SPAC now has to place any initial investor money in a trust or escrow account. This will keep it secure until the sponsors announce their target company. Once that occurs, an investor can back out of the investment if they feel the deal is bad. And SPACs also have to register with the SEC although they do not have to file all the paperwork required in a traditional IPO process.
This lack of transparency means that SPACs are still controversial. When a company goes public via a traditional initial public offering (IPO), they are required to post a series of filings along the way. This gives investors a degree of comfort when investing in the company.