It's the comfort and accessibility that won over a lot of patrons to online gambling platforms. If not for these two, I'm pretty sure people will just look for other hobbies during the pandemic and not try to make a living off of gambling. Plus, the advertisements and marketing strategies of these casinos are also widespread. It reached a lot of audience, and a lot of those may probably already be curious about gambling but are too shy to ask and start with this activity.
Without a doubt those two were very important factors when it comes to getting new customers for casinos, but I also think that another factor was that there was simply nothing to entertain yourself.
As you probably remember most sport events were canceled or delayed, while many movies or TV shows were on the same situation, so people found themselves in a situation in which they had to spent a great deal of their time at home, but at the same time they had nothing to do and they found in gambling a way to pass those difficult months.