The new contract revealed their fear
Immanuel Quickley was a restricted free agent this summer, which meant that they had a significant amount of leverage in negotiations. Not only could they match any deal that Quickley signed elsewhere, but such a deal (an "offer sheet" by the other team) could not be officially signed until a week into free agency, and the Raptors would then have another two days to consider before matching.
Another team would therefore not only have to pay Quickley a large amount to have a shot at signing him, they would have to tie up all of that cap space until July 9th at the earliest, essentially ensuring they couldn't then pivot to add another high-cost player.
The fact that the Raptors couldn't negotiate a more team-friendly contract with Quickley suggests that they had genuine fear that an offer was waiting for Quickley on the open market. Perhaps that was the Orlando Magic or the Detroit Pistons, two teams with a lot of money available and potentially a need at point guard. Would the Utah Jazz have been a stealth possibility? Another team signing Quickley to an offer sheet would have meant a more painful contract to match, one with a likely player option on the fourth year, a trade kicker, or perhaps even a shorter-term deal to put Quickley back on the market even sooner.
If the Raptors know there is no lucrative offer awaiting Quickley they can lean on him more in trade negotiations. Expectations for a new deal fell in the $30 million per year range, or $150 million over five years; he instead made $35 million per season at $175 overall. That difference will matter as the Raptors get significantly more expensive over the next few seasons.