Adobe did not buy Figma at a 50x multiple because it thinks Figma is worth that much. It bought the company at 50x because it was a number Figma's board couldn't say no to, and removes their stiffest competition in a quarter century in the process.
"Why would I use that when I can get figma, XD, or zeplin"
That's a problem they felt was worth $20bln to avoid.