A spike in subscribers for a period doesn't necessarily mean they're making more money than before, even if the number of new signups offsets the cancellations.
I used to pay for the Premium plan, sharing with my parents, but downgraded to the Basic plan. My parents ended up getting their own Basic plan. So a single account essentially split into two, but the sum of both payments is now less than what it used to be for the single account. So Netflix gained an extra subscriber, but is now making less money from that pool of users.
It's totally possible that some number of these new signups consist of people who did the same thing.
Basically, seeing a spike in new signups isn't itself a measure of success. What matters is how much money they're bringing in monthly going forward compared to previously.