Every company in the world does things like this, why do people get upset that Kagi does it as well? Don't you think your local supermarket or electrical company spends money outside of their core business? We're soon in December, when companies will invite their employees to Christmas dinners and other holiday events.
Because a lot of people want Kagi to succeed because they want to keep using the service. So people care if they make bad business decisions that might threaten their long-term success. Compare to, say, Fastmail, who won similar mindshare under similar market circumstances, and who never attempted to enter the real estate business.
That said, this isn't as crazy of an idea as it sounds from the headline. Kagi says they are "remote-first", so the main beneficiary of this real estate is meant to be Kagi and their employees. The idea to open up some of the office space for Kagi customers to reserve is novel but not completely ridiculous either. I can see it working out well as a marketing tool.