Same concept, you buy property with a mortgage, value increases, re-mortgage to release equity to use to buy another property.
Repeat
Only difference, property typically doubles in value every 20 years, Bitcoin typically increases 20 fold every 4 years.
Current wealth of the planet $454T
If Bitcoin 20Xβs twice more, then market cap of Bitcoin will equal total planet wealth.
Therefore $MSTR only has one full halving left till $BTC starts to flatten.