What was the original XFL?

If you lived in the United States in 2001, you likely remember the XFL. During its inaugural season, it was advertised extensively and poised as a viable alternative to the perennially popular NFL. However, the XFL quietly disappeared after 2001. So, what went wrong?

After all, the most recent iteration of the XFL began anew last spring only to be severely impacted — like most 2020 sports — due to the pandemic. However, comparing the 2020 stoppage to 2001's would be like comparing apples to oranges. Was the 2001 incarnation of the XFL a victim of bad timing? Was it a fundamentally flawed concept?

What was the original XFL?