Yeah that's probably part of it but I'd like to think he could have coordinated with the RNC. Good lawyers are also not THAT expensive in the grand scheme of things when your campaign has raised hundreds of millions. His campaign could have just set $25 - $50 million aside rather than use it to pay Brad Parscale's "consulting firm" and that would have lasted for a while.
He probably assumed that he could hire good lawyers on the fly and then didn't have the money for the massive retainer they demanded. No credible law firm would be willing to do work for the Trump campaign without a huge chunk legal fees being funded up front, especially since the major firms have offices in NYC where everyone knows Trump's history of grifting service providers.
His supporters are stupid so they'll never acknowledge it, but the establishment wing of the GOP screwed Trump here. When GWB needed help in 2000, the RNC/Fedsoc deployed an army of conservative lawyers to Florida who were willing to literally stage a riot to prevent votes in Miami-Dade from being counted. This time around the right wing establishment has basically said "We'll stay quiet and delay recognizing Biden as president-elect, but beyond that you're on your own."