offer free deals
build a large customer base very quickly
take a large chunk off competitors' customers
offer much cheaper plans than competition
kill some competitors, make others struggle to survive.
gradually increase tariff. start making profits.
all you need is a large chunk of money, or absurdly low-cost loans, or some govt "assistance", or a mix of these, to last until that "start making profits" line.
I believe they are trying to make money out of other services by commoditizing internet. It seems unlikely that this aggressive pricing is to elbow out of the competitors because in this age, the tech companies normally have short-lived monopoly and long bets don't make much sense.
They also are known for their ways with price competition. Even worse if you are an OEM, delayed payments are the norm.