They don't have to be conservative. It's not their only cash cow. They can experiment.
Instead, they opted to nearly copy Google's UI and leave it at that.
I think they would have done a lot better if they invested in a separate company and gave them freedom + lots of resources, like they did with OpenAI.
I assume it's because Wall Street was mithering them about why they hadn't invented said hit product and they built their own versions just to shut Wall Street up while the Windows/Office money flowed in.
Bing is a remnant from that time that they never killed.
Bing is an insurance policy against Google having too much control over the internet. I don't think Microsoft care about market share, they care about having a foothold that they could invest in if they needed to without needing to go from a standing start.
E.g. Ever tried to get a chat history from a call that's finished with Zoom?
(For example if you search "houses for sale near $placename" it surfaces a property search UX which is actually quite neat. If you type "houses for sale in $placename" which is not exactly an obscure variant query, the same feature is completely hidden (although there is a big button saying "houses for sale" that will reorder your search results without surfacing the house search ui). Battling spam is an ongoing battle, the "best" results are subjective, but not being able to find its own features feels like half-arsed implementation.)
But "house sale $placename" works fwiw!
As for the UI, Microsoft seems to have given up an any type of UI research after the Office ribbon interface lift. I don't know how you'd improve the UI of a search engine, but Bing could stand a bit of improvement, and so could Google.