Failed to install El Capitan

Catalina is not compatible with your hardware: macOS Catalina is compatible with these computers - Apple Support

iMac

Learn how to identify your iMac.

• iMac (Retina 5K, 27-inch, 2019)
• iMac (Retina 4K, 21.5-inch, 2019)
• iMac (Retina 5K, 27-inch, 2017)
• iMac (Retina 4K, 21.5-inch, 2017)
• iMac (21.5-inch, 2017)
• iMac (Retina 5K, 27-inch, Late 2015)
• iMac (Retina 4K, 21.5-inch, Late 2015)
• iMac (21.5-inch, Late 2015)
• iMac (Retina 5K, 27-inch, Mid 2015)
• iMac (Retina 5K, 27-inch, Late 2014)
• iMac (21.5-inch, Mid 2014)
• iMac (27-inch, Late 2013)
• iMac (21.5-inch, Late 2013)
• iMac (27-inch, Late 2012)
• iMac (21.5-inch, Late 2012)

The Maximum MacOS for your computer is 10.11.x

If it is a late 2009 MacBook then according to the following link you should be able to upgrade to High Sierra.

https://support.apple.com/en-us/HT208969

In a 2009 machine, Catalina wouldn't go. I think you need late 2012 and up