I think, in my rather lay opinion, that it takes a lot of up front capital to launch a streaming service...
That up front capital can be offset by long lead times and sustained subscriber growth. Netflix has taken years to build up their streaming service so a lot of their infrastructure is sunk costs and now:
1 - They have a lot of subscribers (more than any other service)
2 - More of that subscriber revenue goes to the bank instead of development costs (productions and servers, etc.)
If you created Netflix today, it wouldn't be profitable over night.
If you look at the older streaming services (I'm looking at you, PlutoTV), you see that they're wildly profitable for the same reasons as Netflix. Which is good, because they don't have diversified revenue streams. If streaming suddenly went belly up tomorrow, they'd have nothing with which to pay the pills.
As a comparison, you have Disney, who had to build their infrastructure (actually bought it by gobbling up MLB's BAMTech) and then had to grow their subscribers rapidly (with massive discounts). Disney+ is still an albatross (Hulu, not so much, because it's been growing for years). But as an old school company, they lean on their diversified portfolio to offset those massive losses (high ticket prices, cruise ships, product licensing, etc.)
Similarly, you have Warner Bros. You have to build HBO Max to make it profitable. But unlike Disney, WB's nestegg was:
1 - Squandered by AT&T
2 - Overcommitted in what was essentially a leveraged by-out
3 - Fell out from under them when a) cable collapsed b) theaters collapsed
I verily expect that WBD's Zaslav thought he could prop up WB with Discovery revenue with little comprehension of what the real challenges were. Discovery launched their own streaming service only months earlier (Discovery+) and it was like Keystone cops, a lesson in how not to launch and operate a streaming service. They didn't have a leg to stand on. Their only hope - and THEY'RE WRONG - is that they can merge their poorly performing streaming service (Discovery+) with HBO Max and leverage the better service with their inferior content. All that's going to do is sink it all.
So, to your initial question... a brave decision years ago by Netflix to slowly pivot towards streaming in a methodical way is what's made them successful, and the only way someone else does the same is if they first invent a time machine.