I think it's reasonable to formulate this as two outcomes (Figma independent and Figma bought by Adobe) and each firm's preferences. From Adobe's standpoint, outcome A has huge tail risk (Figma innovates and eats Adobe's business) so paying a lot for outcome B might be ok. From Figma's POV, they aren't really helped by that tail as much as Adobe is hurt by it (either way they're rich, unless they crash out and become poor), so Figma would love to play it safe and sell the tail gamble. Adobe is paying to buy the high tail and low tail from Figma, but Figma probably doesn't care too much about selling the high tail compared to selling the low tail; meanwhile Adobe mainly wants to buy the high tail. I think it's very reasonable for Adobe to value the high tail at much more than Figma values getting rid of the low tail (Adobe is willing to bid up aggressively while Figma is willing to offer down aggressively).

Whether the government saw Adobe's willingness to overpay for Figma as a signal of Adobe's underlying incentives (as in "I acquire Figma to keep my monopoly" and not "I acquire Figma to vertically integrate and make better product for consumer") seems much harder to speculate on. I didn't explain (nor do I think there's an obvious explanation) for why the original deal was at the high price rather than the low price, but I'd imagine Figma would've been generally willing to sell for less than the price Adobe bid given Adobe was probably Figma's best customer for acquiry.