This is how NOT to install a toilet drain. (Never cut the floor support without reinforcing it).
The toilet was falling into the floor when I arrived here, After removing the old floor I had to replace the floor joists and installed all new plywood.
All the years of having water in the crawl space below the bathroom it rotted the wood floor and damaged the floor joists, I had to tear it all out and replace the supports as well as getting the water out of the crawl. (see sump pump)
I started working on house repairs in my 20’s now I’m in my 60’s and this is by far the most I’ve had to repair, on the bright side it was cheap to purchase and it’s paid for with low taxes.