Spurs need a huge rebuild but Levy is clearly terrified of selling Kane and committing to one.
On the footballing side, take Kane out of that team and things could get really really dark if they don't reinvest very wisely from the get go. That could easily be a bottom half of the table side.
Psychologically, selling Kane and rebuilding is essentially admitting failure on Levy's part. It closes the books on the Harry Kane era as one that was immensely promising and ended in disappointment due to disastrous decisions at club level.
Financially, Harry Kane is the golden goose for Daniel Levy in terms of shirt sales, commercial deals currently being negotiated, etc. I also suspect that much of Tottenham's long term financial planning with the stadium has rested on the assumption that they could establish themselves as a consistent CL side (or that the Super League would happen) and so its probably very tempting to fool yourself into believing that some tweaks around the edges of the squad and a new manager could get a Kane-led club back into the CL, especially with five spots going forward. That's basically the short term wishful thinking Levy has been engaging in for years, its probably very tempting to double down one last time.