On August 1, 2017, at Bitcoin Blockheight #478559, developers, exchanges, miners, and node operators running the Bitcoin Cash software began accepting larger blocks. Stakeholders who continued running the Bitcoin Core software kept the blocksize restricted, later forking to a code change called SegWit on August 24, 2017. Bitcoin Cash (BCH) and Bitcoin Core (BTC) are the two largest bitcoin forks by market cap.
Although some types of transactions take more block space than others, the number of on-chain transactions in each block is directly proportional to blocksize over time.