What's the point of managed switches??

I work at a small MSP and since I have studied for & passed my CCNA last month, I have been able to recognize certain instances at sites where if I knew more, I could make things easier or more efficient..but of course I don't have much experience within the trade. For instance, we have a client who has an office attached to their house and they all share the same network. It was deemed by my bosses that the reason the office was experiencing slow connections within the application they use is because of the switch they were using. That something might have "happened" to it or it went bad. They proceeded to buy 2 switches: 1 for the home network and the other for the office network. I traced the offices lines, plugged each respective line into the dedicated switches and plugged them into the ports I was told to in their firewall.

After everything was all said and done, I come back to the office and asked my supervisor "couldn't we have just made things easier by using one switch and separate the network using VLANS?". He responded "Well, if something were to happen to the switch, such as a shock to the system, the switch would reset & lose all configurations which would cause havoc". I was sitting there thinking to myself....well then by that reasoning, why everything else? Everything in tech is just as susceptible to that scenario. If you propose that scenario, then why even have managed switches?

I recognize that that is an extreme scenario he gave but how realistic is that? Has that ever happened to anyone? Are there way's to mitigate it? Redundancy? Make the switch pull the start-up file from external server? Please help me understand and educate me 🙂 Thank you for your time!