Many tahfiz schools have been mushrooming because there is a business case for such. It used to be Bangladeshis Darul this and Darul that. They set up a school with seed capital and then went round in Malaysia and Saudi and other countries to search for donations.
Now Malaysian Ustazs are using the same business model. They set up a block, a dozen students and then go round to Saudi Arabia, Singapore and Brunei to raise more funds. Otherwise it will never be sustainable.
They survive because there are selfish parents who Hope they will go to heaven if they have a Hafiz son or daughter and there are donors who think they are buying tickets to heaven.