I think this kind of maintenance is still quite reasonable and any casino does the same thing. Stake.com carries out maintenance for a fairly short duration, but regarding developers so far there is no open data regarding the number available or do you have a source regarding the number of developers from each casino?
The maintenance process is a positive thing to maintain player comfort in the future. Here Stake.com is actually routine because they know how many visitors come at the weekend. I used to play at a well known casino on this forum, but the login process was very slow, I even had to refresh several times just to be able to enter. You also need to remember that there are also casinos that are difficult to access and require a VPN so the loading process is 2x slower, requires confirmation, sometimes certain game providers are not available, even though the visitors are not dense, you will definitely be annoyed if you experience a lag in the middle of the game.
The thing is, this is not the first which their server lags during weekends. I experienced a laggy gameplay in almost every weekend of my game here right after when the weekly reload was released.
Stake.com is aware for this scalability issue with their server for long time but they can’t fixed it immediately because they don’t want to fully down their website for the maintenance and let the site still usable during updates even if it’s very laggy.