I was going to ask that too. If the Leafs were weak in Novemeber...they are obviously strong now, but during that transition does it fluctuate with each game? I suppose.
Yes, they all start equal at the beginning of the season. But every win or loss changes their score. If they win many, their score becomes higher and are now considered "strong". If they lose many then their score becomes lower and they become weak. So a team with a high score is expected to win against a team with a lower score. The score then changes based on the difference between the expected result and the actual result
For the leafs example, here is how they fluctuated throughout the season:
Each line shows the date of a game, the teams involved, their game score and the change of elo score before->after the game.
[Date, Visitor (score) before->after, Home (score) before->after ]
[2019-10-02, Ottawa Senators (3): 2500 -> 2450, Toronto Maple Leafs (5): 2500 -> 2550 ]
[2019-10-04, Toronto Maple Leafs (4): 2550 -> 2593, Columbus Blue Jackets (1): 2500 -> 2457 ]
[2019-10-05, Montreal Canadiens (6): 2475 -> 2516, Toronto Maple Leafs (5): 2593 -> 2552 , OTSO]
[2019-10-07, St. Louis Blues (3): 2521 -> 2575, Toronto Maple Leafs (2): 2552 -> 2498 ]
[2019-10-10, Tampa Bay Lightning (7): 2471 -> 2525, Toronto Maple Leafs (3): 2498 -> 2444 ]
[2019-10-12, Toronto Maple Leafs (5): 2444 -> 2513, Detroit Red Wings (2): 2579 -> 2510 ]
[2019-10-15, Minnesota Wild (2): 2409 -> 2374, Toronto Maple Leafs (4): 2513 -> 2548 ]
[2019-10-16, Toronto Maple Leafs (3): 2548 -> 2486, Washington Capitals (4): 2462 -> 2524 ]
[2019-10-19, Boston Bruins (3): 2609 -> 2567, Toronto Maple Leafs (4): 2486 -> 2528 , OTSO]
[2019-10-21, Columbus Blue Jackets (4): 2474 -> 2507, Toronto Maple Leafs (3): 2528 -> 2495 , OTSO]
[2019-10-22, Toronto Maple Leafs (2): 2495 -> 2455, Boston Bruins (4): 2567 -> 2607 ]
[2019-10-25, San Jose Sharks (1): 2530 -> 2469, Toronto Maple Leafs (4): 2455 -> 2516 ]
[2019-10-26, Toronto Maple Leafs (2): 2516 -> 2453, Montreal Canadiens (5): 2422 -> 2485 ]
[2019-10-29, Washington Capitals (4): 2620 -> 2623, Toronto Maple Leafs (3): 2453 -> 2450 , OTSO]
[2019-11-02, Toronto Maple Leafs (4): 2450 -> 2479, Philadelphia Flyers (3): 2481 -> 2452 , OTSO]
[2019-11-05, Los Angeles Kings (1): 2359 -> 2326, Toronto Maple Leafs (3): 2479 -> 2512 ]
[2019-11-07, Vegas Golden Knights (1): 2517 -> 2491, Toronto Maple Leafs (2): 2512 -> 2538 , OTSO]
[2019-11-09, Philadelphia Flyers (3): 2547 -> 2571, Toronto Maple Leafs (2): 2538 -> 2514 , OTSO]
[2019-11-10, Toronto Maple Leafs (4): 2514 -> 2450, Chicago Blackhawks (5): 2414 -> 2478 ]
[2019-11-13, Toronto Maple Leafs (4): 2450 -> 2433, New York Islanders (5): 2721 -> 2738 ]
[2019-11-15, Boston Bruins (4): 2521 -> 2559, Toronto Maple Leafs (2): 2433 -> 2395 ]
[2019-11-16, Toronto Maple Leafs (1): 2395 -> 2355, Pittsburgh Penguins (6): 2467 -> 2507 ]
[2019-11-19, Toronto Maple Leafs (2): 2355 ->
2310, Vegas Golden Knights (4): 2388 -> 2433 ]
[2019-11-21, Toronto Maple Leafs (3): 2310 -> 2390, Arizona Coyotes (1): 2556 -> 2476 ]
[2019-11-23, Toronto Maple Leafs (5): 2390 -> 2454, Colorado Avalanche (3): 2493 -> 2429 ]
[2019-11-27, Toronto Maple Leafs (6): 2454 -> 2481, Detroit Red Wings (0): 2278 -> 2251 ]
[2019-11-29, Toronto Maple Leafs (4): 2481 -> 2415, Buffalo Sabres (6): 2363 -> 2429 ]
[2019-11-30, Buffalo Sabres (1): 2429 -> 2402, Toronto Maple Leafs (2): 2415 -> 2442 , OTSO]
[2019-12-03, Toronto Maple Leafs (1): 2442 -> 2413, Philadelphia Flyers (6): 2595 -> 2624 ]
[2019-12-04, Colorado Avalanche (3): 2598 -> 2624, Toronto Maple Leafs (1): 2413 -> 2387 ]
[2019-12-07, Toronto Maple Leafs (5): 2387 -> 2462, St. Louis Blues (2): 2577 -> 2502 ]
[2019-12-10, Toronto Maple Leafs (4): 2462 -> 2514, Vancouver Canucks (1): 2473 -> 2421 ]
[2019-12-12, Toronto Maple Leafs (2): 2514 -> 2481, Calgary Flames (4): 2634 -> 2667 ]
[2019-12-14, Toronto Maple Leafs (4): 2481 -> 2517, Edmonton Oilers (1): 2380 -> 2344 ]
[2019-12-17, Buffalo Sabres (3): 2518 -> 2468, Toronto Maple Leafs (5): 2517 -> 2567 ]
[2019-12-20, Toronto Maple Leafs (6): 2567 -> 2597, New York Rangers (3): 2423 -> 2393 ]
[2019-12-21, Detroit Red Wings (1): 2310 -> 2294, Toronto Maple Leafs (4): 2597 -> 2613 ]
[2019-12-23, Carolina Hurricanes (6): 2649 -> 2594, Toronto Maple Leafs (8): 2613 -> 2668 ]
[2019-12-27, Toronto Maple Leafs (5): 2668 -> 2664, New Jersey Devils (4): 2438 -> 2442 , OTSO]
[2019-12-28, New York Rangers (5): 2486 -> 2535, Toronto Maple Leafs (4): 2664 -> 2615 , OTSO]
[2019-12-31, Toronto Maple Leafs (4): 2615 -> 2653, Minnesota Wild (1): 2529 -> 2491 ]
[2020-01-02, Toronto Maple Leafs (6): 2653 ->
2684, Winnipeg Jets (3): 2514 -> 2483 ]