I once had to demolish kitchen counters done like this. We had just moved in and there was blackness between the ceramic tiles on the counter top. So I put bleach water over the area and let it set. Came back and there was no water on the counter. I opened the drawer and found the water there. The grout had long ago failed and the wood was rotted all the way through. We were young and strong then and it was almost too much for us to demolish it using sledgehammer, pry bars, and chisels.

Someone once told me they used a mini jack hammer to remove till in a 50's bathroom.

Yep. But from the sound of it here, there weren't nuthin 'mini' about it.

Real life ain’t like hgtv. Those rubble set tile bathrooms were meant to last. Unfortunately they usually shortened the joists, notched them, and eventually someone let the plumbing leak. Ugh. So after all this comes out the whole floor gets reframed. ‘My internet research says I should be able to get my whole bathroom remodeled for $10,000?!’ Nope!

My 100+ y.o. Farmhouse has a notched joist! No leaks etc in the bathroom I gutted, just was 'time' and fixing an unfortunate placement. However, they did find rot below the rubble...not sure how long it would have lasted before I had a surprise trip to the basement!!